Hi Comunity. Before I describe the problem I should note I own my mobile subscription for many years, approximately since 2017, I used many different mobile routers both stationary and portable during this time. I have several sim-cards connected to the subscription, which I use in  my phone and in couple of mobile routers and, since a week ago with Deco X50 5G. Again, I never  had the below problem with other devices!
So, I have an unlimited subscription from Tele2 in Sweden. The subscription works as follows: after 50GB per day, one most send a short sms to extended it by 5 GB, one can do this unlimited times and these 5G extension can be accumulated.One can send this 5GB  extension  SMS in advance, so when 50GB has gone, it just starts using the next 5GB extension. This 50 GB limit is reset 00:00 each day. Everything works well with X50-5G. However IF the 50GB limit has been reached and I am using 5GB extension exactly at 00:00 when the limit is reset the X50-5G looses connection until I restart the router. It does not restore the connection even half an hour after 00:00.
So, again, only those days when 50GB limit was reached and I am using extensions the connection is lost at 00:00. I have noticed this already 3 times. Never had this with other routers or with my phone. I really like the router, but this problem is very annoying.