[ONE Q&A, Help & Troubleshooting] ze7zez:
I'm sad. The error may be in the damaged partition.

There are quite a lot of them.

You will see the list of partitions:

ls -l /dev/block/platform/msm_sdcc.1/by-name/

We'll start by repairing the Cache, System, Data partitions

1. The first variant, the least drastic:

Wipe -> Advanced Wipe -> select Cache -> Repair or Change File System -> Repair File System -> Swipe to Repair

Wipe -> Advanced Wipe -> select System -> Repair or Change File System -> Repair File System -> Swipe to Repair

Wipe -> Advanced Wipe -> select Data -> Repair or Change File System -> Repair File System -> Swipe to Repair

TWRP -> Install -> os.zip

TWRP -> Reboot -> System

2. The second variant. Reformatting the partition and return to the original.

Wipe -> Advanced Wipe -> select Cache -> Repair or Change File System -> Change File System -> select exFat -> Swipe to Repair

Wipe -> Advanced Wipe -> select System -> Repair or Change File System -> Change File System -> select exFat -> Swipe to Repair

Wipe -> Advanced Wipe -> select Data -> Repair or Change File System -> Change File System -> select exFat -> Swipe to Repair

Wipe -> Advanced Wipe -> select Cache -> Repair or Change File System -> Change File System -> select EXT4 -> Swipe to Repair

Wipe -> Advanced Wipe -> select System -> Repair or Change File System -> Change File System -> select EXT4 -> Swipe to Repair

Wipe -> Advanced Wipe -> select Data -> Repair or Change File System -> Change File System -> select EXT4 -> Swipe to Repair

TWRP -> Install -> os.zip

TWRP -> Reboot -> System

If it still does not help and the installation does not finish correctly, we take the next step.

3. Until now, the assumption was that the error could be in System, Data and Cache partitions

If the ROM is correctly installed,

then the boot partition is full of the kernel that starts the android.

In your case, the kernel does not even start.

If the kernel were running, the screen would hang on the Oneplus logo.

Let's try to check the TWRP operation from the boot partition.

Now we move on to the more difficult task.

Read several times from start to finish.

Activities are risky.

Because the reason for the continuous reboot to TWRP is unknown,

you may lose access to TWRP and will not do without replacing the usb socket.

Fortunately, we do not touch the booloader partition, so after getting a working usb socket you will be able to re-upload what you need.

You should perform a full backup of important partitions:

cd /sdcard
dd if=/dev/block/platform/msm_sdcc.1/by-name/boot of=boot.img
dd if=/dev/block/platform/msm_sdcc.1/by-name/recovery of=recovery.img

Resetting the boot partition and loading TWRP recovery to it:

cd /sdcard
dd if=/dev/zero of=/dev/block/platform/msm_sdcc.1/by-name/boot
dd if=recovery.img of=/dev/block/platform/msm_sdcc.1/by-name/boot
reboot boot

If TWRP starts, it's okay, because it means the boot partition is good.

If not, we have the culprit.

Resetting the recovery partition and flashing recovery to it:

cd /sdcard
dd if=/dev/zero of=/dev/block/platform/msm_sdcc.1/by-name/recovery
dd if=recovery.img of=/dev/block/platform/msm_sdcc.1/by-name/recovery
reboot recovery

Again, we're in TWRP located in the recovery partition, so:

Advanced Wipe: System, Data, Cache

TWRP -> Install -> os.zip

TWRP -> Reboot -> System

If you are still unsuccessful, then record a boot movie and describe the next steps you will see on the OPO screen with millisecond accuracy.