Flint - site-to-site breaks: Device XXX LAN IP or routes changed, stop and then start network to take effect

Hi,
I’m using 2 Flint GL-AX1800 (call it like “01” and “02”) at different locations, connected site-to-site (goodcloud.xyz).
Before updating to 4.4.60 sometimes this connections was dead. Restarting on goodcloud was successfull. Can’t say why this site-to-site failed sometimes.
After update to 4.4.60 site-to-site connection fails daily with this message on goodcloud:

Device 02 LAN IP or routes changed, stop and then start network to take effect.

On device 01 nothing was changed, no configuration items. Only: nightly WLAN ist switched off automatically. One day a week at 03.00 PM it takes a job to reboot.
What could cause such a message and changing?

Are they both on the same physical network, like one upstairs and one downstairs or no?

Are they both on the same physical network, like one upstairs and one downstairs or no?

No, different locations (next village). Both Flints create there own VDSL-connection with public IP.

Today ca. 03:00 PM: Peng, site-to-site breaks … ;-((( (like every night)