[OnePlus 12] crossmxn:
just checked the logs from Fastboot Enhance and this is what I'm getting when trying to flash slot B with the same payload.bin that I used for A:

Extracting system

Extracted system

Extracting system_ext

Extracted system_ext

Extracting product

Extracted product

Extracting vbmeta_system

Extracted vbmeta_system

Extracting boot

Extracted boot

Extracting init_boot

Extracted init_boot

Extracting vendor_boot

Extracted vendor_boot

Extracting recovery

Extracted recovery

Extracting vendor

Extracted vendor

Extracting vendor_dlkm

Extracted vendor_dlkm

Extracting system_dlkm

Extracted system_dlkm

Extracting odm

Extracted odm

Extracting dtbo

Extracted dtbo

Extracting vbmeta

Extracted vbmeta

Extracting abl

Extracted abl

Extracting aop

Extracted aop

Extracting aop_config

Extracted aop_config

Extracting bluetooth

Extracted bluetooth

Extracting cpucp

Extracted cpucp

Extracting devcfg

Extracted devcfg

Extracting dsp

Extracted dsp

Extracting engineering_cdt

Extracted engineering_cdt

Extracting featenabler

Extracted featenabler

Extracting hyp

Extracted hyp

Extracting imagefv

Extracted imagefv

Extracting keymaster

Extracted keymaster

Extracting modem

Extracted modem

Extracting oplus_sec

Extracted oplus_sec

Extracting oplusstanvbk

Extracted oplusstanvbk

Extracting qupfw

Extracted qupfw

Extracting shrm

Extracted shrm

Extracting splash

Extracted splash

Extracting tz

Extracted tz

Extracting uefi

Extracted uefi

Extracting uefisecapp

Extracted uefisecapp

Extracting cpucp_dtb

Extracted cpucp_dtb

Extracting vbmeta_vendor

Extracted vbmeta_vendor

Extracting xbl

Extracted xbl

Extracting xbl_config

Extracted xbl_config

Extracting xbl_ramdump

Extracted xbl_ramdump

Extracting my_product

Extracted my_product

Extracting my_engineering

Extracted my_engineering

Extracting my_stock

Extracted my_stock

Extracting my_carrier

Extracted my_carrier

Extracting my_region

Extracted my_region

Extracting my_bigball

Extracted my_bigball

Extracting my_heytap

Extracted my_heytap

Extracting my_manifest

Extracted my_manifest

Invalid sparse file format at header magic

Sending sparse 'system' 1/3 (262140 KB) OKAY [ 7.025s]

Writing 'system' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Invalid sparse file format at header magic

Sending sparse 'system_ext' 1/4 (262140 KB) OKAY [ 7.123s]

Writing 'system_ext' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'product' (6072 KB) OKAY [ 0.173s]

Writing 'product' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'vbmeta_system_b' (8 KB) OKAY [ 0.000s]

Writing 'vbmeta_system_b' OKAY [ 0.000s]

Finished. Total time: 0.016s

Sending 'boot_b' (196608 KB) OKAY [ 5.313s]

Writing 'boot_b' OKAY [ 0.064s]

Finished. Total time: 5.987s

Sending 'init_boot_b' (8192 KB) OKAY [ 0.225s]

Writing 'init_boot_b' OKAY [ 0.000s]

Finished. Total time: 0.241s

Sending 'vendor_boot_b' (196608 KB) OKAY [ 5.270s]

Writing 'vendor_boot_b' OKAY [ 0.058s]

Finished. Total time: 5.338s

Sending 'recovery_b' (102400 KB) OKAY [ 2.816s]

Writing 'recovery_b' OKAY [ 0.031s]

Finished. Total time: 2.853s

Invalid sparse file format at header magic

Sending sparse 'vendor' 1/5 (262140 KB) OKAY [ 7.249s]

Writing 'vendor' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'vendor_dlkm' (29676 KB) OKAY [ 0.822s]

Writing 'vendor_dlkm' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'system_dlkm' (7184 KB) OKAY [ 0.204s]

Writing 'system_dlkm' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Invalid sparse file format at header magic

Sending sparse 'odm' 1/7 (262140 KB) OKAY [ 7.205s]

Writing 'odm' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'dtbo_b' (24576 KB) OKAY [ 0.665s]

Writing 'dtbo_b' OKAY [ 0.015s]

Finished. Total time: 0.681s

Sending 'vbmeta_b' (8 KB) OKAY [ 0.000s]

Writing 'vbmeta_b' OKAY [ 0.000s]

Finished. Total time: 0.011s

Sending 'abl_b' (272 KB) OKAY [ 0.011s]

Writing 'abl_b' OKAY [ 0.000s]

Finished. Total time: 0.021s

Sending 'aop_b' (328 KB) OKAY [ 0.013s]

Writing 'aop_b' OKAY [ 0.000s]

Finished. Total time: 0.020s

Sending 'aop_config_b' (28 KB) OKAY [ 0.000s]

Writing 'aop_config_b' OKAY [ 0.000s]

Finished. Total time: 0.008s

Sending 'bluetooth_b' (1404 KB) OKAY [ 0.037s]

Writing 'bluetooth_b' OKAY [ 0.005s]

Finished. Total time: 0.053s

Sending 'cpucp_b' (248 KB) OKAY [ 0.009s]

Writing 'cpucp_b' OKAY [ 0.004s]

Finished. Total time: 0.020s

Sending 'devcfg_b' (60 KB) OKAY [ 0.000s]

Writing 'devcfg_b' OKAY [ 0.000s]

Finished. Total time: 0.002s

Sending 'dsp_b' (65536 KB) OKAY [ 1.770s]

Writing 'dsp_b' OKAY [ 0.033s]

Finished. Total time: 1.803s

Sending 'engineering_cdt_b' (1024 KB) OKAY [ 0.026s]

Writing 'engineering_cdt_b' OKAY [ 0.006s]

Finished. Total time: 0.039s

Sending 'featenabler_b' (104 KB) OKAY [ 0.000s]

Writing 'featenabler_b' OKAY [ 0.000s]

Finished. Total time: 0.004s

Sending 'hyp_b' (1528 KB) OKAY [ 0.050s]

Writing 'hyp_b' OKAY [ 0.001s]

Finished. Total time: 0.058s

Sending 'imagefv_b' (96 KB) OKAY [ 0.001s]

Writing 'imagefv_b' OKAY [ 0.000s]

Finished. Total time: 0.015s

Sending 'keymaster_b' (416 KB) OKAY [ 0.016s]

Writing 'keymaster_b' OKAY [ 0.000s]

Finished. Total time: 0.023s

Invalid sparse file format at header magic

Sending sparse 'modem_b' 1/1 (207596 KB) OKAY [ 5.901s]

Writing 'modem_b' OKAY [ 0.555s]

Finished. Total time: 6.907s

Sending 'oplus_sec_b' (852 KB) OKAY [ 0.016s]

Writing 'oplus_sec_b' OKAY [ 0.000s]

Finished. Total time: 0.029s

Sending 'oplusstanvbk_b' (4236 KB) OKAY [ 0.121s]

Writing 'oplusstanvbk_b' OKAY [ 0.004s]

Finished. Total time: 0.143s

Sending 'qupfw_b' (60 KB) OKAY [ 0.002s]

Writing 'qupfw_b' OKAY [ 0.002s]

Finished. Total time: 0.018s

Sending 'shrm_b' (136 KB) OKAY [ 0.000s]

Writing 'shrm_b' OKAY [ 0.006s]

Finished. Total time: 0.021s

Sending 'splash_b' (14716 KB) OKAY [ 0.411s]

Writing 'splash_b' OKAY [ 0.015s]

Finished. Total time: 0.431s

Sending 'tz_b' (4028 KB) OKAY [ 0.112s]

Writing 'tz_b' OKAY [ 0.016s]

Finished. Total time: 0.143s

Sending 'uefi_b' (3084 KB) OKAY [ 0.071s]

Writing 'uefi_b' OKAY [ 0.015s]

Finished. Total time: 0.102s

Sending 'uefisecapp_b' (196 KB) OKAY [ 0.006s]

Writing 'uefisecapp_b' OKAY [ 0.000s]

Finished. Total time: 0.012s

Sending 'cpucp_dtb_b' (16 KB) OKAY [ 0.000s]

Writing 'cpucp_dtb_b' OKAY [ 0.000s]

Finished. Total time: 0.016s

Sending 'vbmeta_vendor_b' (4 KB) OKAY [ 0.000s]

Writing 'vbmeta_vendor_b' OKAY [ 0.000s]

Finished. Total time: 0.003s

Sending 'xbl_b' (1072 KB) OKAY [ 0.032s]

Writing 'xbl_b' OKAY [ 0.000s]

Finished. Total time: 0.037s

Sending 'xbl_config_b' (224 KB) OKAY [ 0.000s]

Writing 'xbl_config_b' OKAY [ 0.012s]

Finished. Total time: 0.020s

Sending 'xbl_ramdump_b' (856 KB) OKAY [ 0.013s]

Writing 'xbl_ramdump_b' OKAY [ 0.000s]

Finished. Total time: 0.048s

Invalid sparse file format at header magic

Sending sparse 'my_product' 1/3 (262140 KB) OKAY [ 7.250s]

Writing 'my_product' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'my_engineering' (328 KB) OKAY [ 0.013s]

Writing 'my_engineering' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Invalid sparse file format at header magic

Sending sparse 'my_stock' 1/5 (262140 KB) OKAY [ 7.783s]

Writing 'my_stock' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'my_carrier' (328 KB) OKAY [ 0.005s]

Writing 'my_carrier' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'my_region' (732 KB) OKAY [ 0.023s]

Writing 'my_region' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Invalid sparse file format at header magic

Sending sparse 'my_bigball' 1/4 (262140 KB) OKAY [ 7.748s]

Writing 'my_bigball' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Invalid sparse file format at header magic

Sending sparse 'my_heytap' 1/4 (262140 KB) OKAY [ 7.218s]

Writing 'my_heytap' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed

Sending 'my_manifest' (344 KB) OKAY [ 0.005s]

Writing 'my_manifest' FAILED (remote: 'No such file or directory')

fastboot: error: Command failed