Hi,
I've been looking for similar problem on forum but all are a bit different.
I was runninng BOINC (7.14.2) on Raspberry Pi (Raspbian OS) for few weeks and everything was fine. Recently after starting BOINC it connects to the client, the projects and task are shown but after a minute or so all disappears and "connecting to localhost" is shown. Then it gets connected, everything is shown againg and the cycle repeats. At the end the message is shown "The BOINC client has exited inexpectedly 3 times within last 5 min..." If I restart it all starts again as written above.
I'm running quite a lot of projects but I suspended them for now.
Any help diagnosting the client? I'm a noob a linux so detailed instructons would be fine :)

Too much cpu or memory pressure running too many simultaneous projects leading to the client crashing and causing the Manager to lose connection to the client.

Start BOINC again with a single project enabled. See if it is stable. Then add another project and check again. Keep adding projects until the problem appears again the last project enabled probably is the culprit causing the instability. Check with that project alone to further isolate it being the culprit.

I'm left with one project that I can't remove (the button is not active) but this changed nothing. I think this project was unactive for a quite long and I can't see this host machine on project website so I think it is not resposnible for the problem.

'Remove button inactive' usually results when a project has been added by an 'Account Manager'. Do you now use, or have you ever used, an account manager on that machine?

Yes I'm am using BAM! I removed this project from BAM! Account Manager but BOINC fails to communicate with the AM. I think the period when the connection to client is active is too short for RPi to communicate with BAM!

I disconnected the Account Menager and now I have an empty project list. This didn't fix the issue. I still get the message that client has exitet 3 times in x minutes. The only difference is the popup window to choose new project.
I think I will have to reinstall...