AWS Client no longer responding connection closed

We have a couple of servers running on AWS. As of the middle of last week we suddenly are having connection problems. The server logs mostly lists error 10, sometimes error 51. These customers have poor internet connection, so we have set up a server and a client in the cloud. The users connects to the client through an RDP session. It is a Windows enviroment with one customer using Windows server 12 and FMS 14, the other Windows server 16 and FMS15. We use a seperate AD server to control the RDP access and accounts to the FMP server, clients have no acces to the FMS server.

I have read previous posts on this issue. I do not think there can be any hardware issue, since the server is hosted with Amazon and both server and client are on an internal network. To be sure I have filed a support request with Amazon as well.

The strange thing is that the error message sometimes occurs within a minute and then FMP freezes on the user while they are still working in the FM app. It is my understanding that error 10 occurs if the client does not respond to the server ping for 2 pings, so time out for this error should be 125 seconds. 

These servers have been running without this issue for a long time now. Any idea why this has suddenly changed and why the error message errors while tghe users is using the FM app?