I did
fastboot flash boot boot.img
fastboot flash dtbo dtbo.img
fastboot flash recovery recovery.img
fastboot flash vbmeta vbmeta.img
fastboot flash vbmeta_system vbmeta_system.img
fastboot reboot fastboot
fastboot flash system system.img
fastboot flash system_ext system_ext.img
fastboot flash product product.img
fastboot flash odm odm.img
fastboot flash vendor vendor.img
fastboot reboot recovery
Worked for me
Thanx for your reply MariusKv. I try that tomorrow and post the result here ;-)
############################UPDATE##################################
Hi MariusKv,
I did the steps you sugested in your post. It did not work for me. My phone reboots to Fastbootmode. Is there something else that can solve my problem?
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash boot boot.img
target reported max download size of 805306368 bytes
sending 'boot_b' (98304 KB)...
OKAY [ 4.070s]
writing 'boot_b'...
OKAY [ 0.284s]
finished. total time: 4.354s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash dtbo dtbo.img
target reported max download size of 805306368 bytes
sending 'dtbo' (8192 KB)...
OKAY [ 0.489s]
writing 'dtbo'...
OKAY [ 0.027s]
finished. total time: 0.516s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash recovery recovery.img
target reported max download size of 805306368 bytes
sending 'recovery' (102400 KB)...
OKAY [ 5.525s]
writing 'recovery'...
OKAY [ 0.354s]
finished. total time: 5.879s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash vbmeta vbmeta.img
target reported max download size of 805306368 bytes
sending 'vbmeta' (8 KB)...
OKAY [ 0.021s]
writing 'vbmeta'...
OKAY [ 0.003s]
finished. total time: 0.024s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash vbmeta_system vbmeta_system.img
target reported max download size of 805306368 bytes
sending 'vbmeta_system' (4 KB)...
OKAY [ 0.016s]
writing 'vbmeta_system'...
OKAY [ 0.003s]
finished. total time: 0.019s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot reboot fastboot
fastboot: usage: unknown reboot target fastboot
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash system system.img
target reported max download size of 805306368 bytes
Invalid sparse file format at header magic
sending sparse 'system' 1/3 (784964 KB)...
OKAY [ 45.485s]
writing 'system' 1/3...
FAILED (remote: Partition not found)
finished. total time: 45.508s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash system_ext system_ext.img
error: cannot load 'system_ext.img': No such file or directory
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash product product.img
target reported max download size of 805306368 bytes
Invalid sparse file format at header magic
sending sparse 'product' 1/2 (785388 KB)...
OKAY [ 45.049s]
writing 'product' 1/2...
FAILED (remote: Partition not found)
finished. total time: 45.051s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash odm odm.img
target reported max download size of 805306368 bytes
sending 'odm' (960 KB)...
OKAY [ 0.092s]
writing 'odm'...
FAILED (remote: (odm_b) No such partition)
finished. total time: 0.095s
sakasakaheyhey@Wan-Bigi-Kiskissie:~/Downloads/10.5.12-EUROPE-OnePlus8ProOxygen_15.E.21_OTA_021_all_2008080100
_c953-FASTBOOT$ fastboot flash vendor vendor.img
target reported max download size of 805306368 bytes
Invalid sparse file format at header magic
sending sparse 'vendor' 1/2 (785429 KB)...
OKAY [ 46.612s]
writing 'vendor' 1/2...
FAILED (remote: Partition not found)
finished. total time: 46.615s