[Google Pixel 3a Questions & Answers] simhagen:
Ok, so far so good. I tried it on Windows with the newest version, same problem. Than I switched to Linux and it worked up to the point "Sending sparse 'vendor_b' 1/3 (262140 KB)" than it gets stuck and nothing happens.

[xxx@xxx-pc MyApplication]$ sudo fastboot flash bootloader /home/XXXX/Downloads/sargo-pd2a.190115.029/bootloader-sargo-b4s4-0.1-5262905.img
Sending 'bootloader_b' (8349 KB) OKAY [ 0.340s]
Writing 'bootloader_b' (bootloader) Flashing Pack version b4s4-0.1-5262905
(bootloader) Flashing partition table for Lun = 0
(bootloader) Flashing partition xbl_b
(bootloader) Flashing partition xbl_config_b
(bootloader) Flashing partition tz_b
(bootloader) Flashing partition aop_b
(bootloader) Flashing partition hyp_b
(bootloader) Flashing partition keymaster_b
(bootloader) Flashing partition cmnlib_b
(bootloader) Flashing partition cmnlib64_b
(bootloader) Flashing partition abl_b
(bootloader) Flashing partition devcfg_b
(bootloader) Flashing partition qupfw_b
(bootloader) Flashing partition storsec_b
OKAY [ 0.541s]
Finished. Total time: 1.074s
[xxx@xxx-pc MyApplication]$ sudo fastboot reboot bootloader
Rebooting into bootloader OKAY [ 0.015s]
Finished. Total time: 0.065s
[xxx@xxx-pc MyApplication]$ sudo fastboot flash radio /home/XXXX/Downloads/sargo-pd2a.190115.029/radio-sargo-g670-00011-190213-b-5306579.img
Sending 'radio_b' (72988 KB) OKAY [ 2.230s]
Writing 'radio_b' (bootloader) Flashing Pack version SSD:g670-00011-190213-B-5306579
(bootloader) Flashing partition modem_b
OKAY [ 0.880s]
Finished. Total time: 3.315s
[xxx@xxx-pc MyApplication]$ sudo fastboot reboot bootloader
Rebooting into bootloader OKAY [ 0.015s]
Finished. Total time: 0.065s
[xxx@xxx-pc MyApplication]$ sudo fastboot update -w /home/XXXX/Downloads/sargo-pd2a.190115.029/image-sargo-pd2a.190115.029.zip
--------------------------------------------
Bootloader Version...: b4s4-0.1-5262905
Baseband Version.....: g670-00011-190213-B-5306579
Serial Number........: xxxxxx
--------------------------------------------
extracting android-info.txt (0 MB) to RAM...
Checking 'product' OKAY [ 0.051s]
Checking 'version-bootloader' OKAY [ 0.052s]
Checking 'version-baseband' OKAY [ 0.052s]
Setting current slot to 'b' OKAY [ 0.063s]
extracting boot.img (64 MB) to disk... took 0.284s
archive does not contain 'boot.sig'
Sending 'boot_b' (65536 KB) OKAY [ 1.990s]
Writing 'boot_b' OKAY [ 0.729s]
extracting dtbo.img (8 MB) to disk... took 0.056s
archive does not contain 'dtbo.sig'
Sending 'dtbo_b' (8192 KB) OKAY [ 0.340s]
Writing 'dtbo_b' OKAY [ 0.133s]
archive does not contain 'dt.img'
archive does not contain 'recovery.img'
extracting vbmeta.img (0 MB) to disk... took 0.000s
archive does not contain 'vbmeta.sig'
Sending 'vbmeta_b' (4 KB) OKAY [ 0.120s]
Writing 'vbmeta_b' OKAY [ 0.064s]
archive does not contain 'vbmeta_system.img'
archive does not contain 'vendor_boot.img'
archive does not contain 'super_empty.img'
archive does not contain 'boot_other.img'
archive does not contain 'odm.img'
archive does not contain 'product.img'
extracting system.img (2271 MB) to disk... took 11.015s
archive does not contain 'system.sig'
Sending sparse 'system_b' 1/9 (262140 KB) OKAY [ 7.389s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 2/9 (262140 KB) OKAY [ 7.840s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 3/9 (262140 KB) OKAY [ 7.830s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 4/9 (262140 KB) OKAY [ 7.760s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 5/9 (262140 KB) OKAY [ 7.870s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 6/9 (262140 KB) OKAY [ 7.810s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 7/9 (262140 KB) OKAY [ 7.810s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 8/9 (258620 KB) OKAY [ 7.690s]
Writing 'system_b' OKAY [ 0.370s]
Sending sparse 'system_b' 9/9 (232288 KB) OKAY [ 7.020s]
Writing 'system_b' OKAY [ 1.920s]
archive does not contain 'system_ext.img'
extracting system_other.img (391 MB) to disk... took 1.914s
archive does not contain 'system.sig'
Sending sparse 'system_a' 1/2 (262140 KB) OKAY [ 7.850s]
Writing 'system_a' OKAY [ 0.370s]
Sending sparse 'system_a' 2/2 (138668 KB) OKAY [ 4.200s]
Writing 'system_a' OKAY [ 1.380s]
extracting vendor.img (523 MB) to disk... took 2.502s
archive does not contain 'vendor.sig'
Sending sparse 'vendor_b' 1/3 (262140 KB)