HA bricking FritzBox 6600?

Hi all,

I have strange problem. 10 days ago my internet provider switched my router to FritzBox 6600 - Cable modem. From that day I have issues with router. I’m loosing internet connection every 10min to few hours time.
I tried bunch of things and involved technicians from internet provider. They said to me that I turning of one by one device in my network. And after 10 days I turned off HA and from that, I didn’t have single outage. Today I turned on HA and problem appeared again.

I checked logs in Fritzbox and nothing smart in them (user logs are shit). Ill try to check HA and Fritz network traffic with Wireshark, but Im without ideas. Ill report findings to my internet provider but I don’t think there will be a will to resolve this from their side.

HA is VM in HyperV. Latest version. Nothing special in it, few sensors, Zigbee bridge (Sonoff flashed with tasmota).

Any thoughts, suggestions or something? Thank you.

Cheers from Croatia.