I had a similar issue with using tail scale, but here the issue was definitely not on the client. My actual DSL connection would reset, multiple times per day. Had the provider come 4 times to investigate the issue, got 3 new routers, they reinstalled the entry point to the house, and fixed an issue in the neighbourhood central point. All to no avail. I ended up purging everything tail scale and hand rolled wireguard. No more issues :/