If you read carefully is says:" You can't downgrade from 1.1.1 to 1.0.x, so you have to stay on existing firmware or upgrade.

@ChrisBS I agree with this what you mention and added in your post. Same issue with copying files.

@David6479 it could be beta firmware. But this is what tp-link tech support send me to email. I didn't look closer detailed.

@GrenSo firmware version: 1.1.1 Build 20241230 rel.20267(4555), I don't anything new or different.

Ok, TP-Link support sent me (service (prerelease)) firmware, I'll going to try now. Does it fix or not. UPDATE. Works perfect no reboots yet.

So I turned router in AP Mode (Bridge Mode). Attached Nokia Streaming Box 8000 via ethernet cable to Sky Router and no issues. (I can access everything to local network). For now TP-Link router works...