seems like u dirty flash from A12 & it doesn't work.
i initially also wanted to try dirty flash like u did, coz for some ROM, it works.
but as pointed out, dirty flash doesn't work for A13.
i suggest u follow the following steps:
1. MSM tool your device to stock.
2. Update to latest OOS12 version.
3. Enable USB debugging, unlock bootloader.
4. Flash to older dtbo.img & vendor_boot.img
5. Flash recovery.img to LineageOS recovery.
6. Reboot into recovery.
7. adb sideload copy-partitions-20210323_1922.zip
*this is to make sure latest OS is installed on both partition*
8. Reboot again back into recovery, factory reset.
9. adb sideload nameless_A13_rom.zip
10. adb sideload Magisk-v25.2.zip if u wish to root.
11. Done! reboot into system.