Hello everyone, I just want to put my updates on this topic. I have tried disable journal as @ffr2822 suggested and it looks good for start, I was able to reboot my router and backup still works. But...

Thank You @ffr2822! I'll give it a try, hopefully it can fix this annoying bug

Hello, I have Archer AX6000 with enabled Time machine and with connected my 2TB WD external hardrive. Disk is formated ad HFS and connected to router via USB-C connector. Time machine backups works...