There are multiple errors in the buildbot server logs. I'm not sure if it's related or not.

2020-08-28 09:16:25+0000 [-] while invoking <bound method HttpStatusPushBase.buildStarted of <buildbot.reporters.github.GitHubStatusPush object at 0x7f661dd58850>>
	Traceback (most recent call last):
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
	    result = g.send(result)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/buildbot/reporters/http.py", line 80, in getMoreInfoAndSend
	    yield self.send(build)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 1613, in unwindGenerator
	    return _cancellableInlineCallbacks(gen)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 1529, in _cancellableInlineCallbacks
	    _inlineCallbacks(None, g, status)
	--- <exception caught here> ---
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/buildbot/reporters/http.py", line 80, in getMoreInfoAndSend
	    yield self.send(build)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
	    result = g.send(result)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/buildbot/reporters/github.py", line 133, in send
	    m = re.search(r"refs/pull/([0-9]*)/merge", branch)
	  File "/usr/lib/python3.8/re.py", line 201, in search
	    return _compile(pattern, flags).search(string)
	builtins.TypeError: expected string or bytes-like object


Error when stopping the server. It seems like this one is just that a client tries to reconnect whereas the server is down:

2020-08-28 09:30:43+0000 [HTTP11ClientProtocol (TLSMemoryBIOProtocol),client] BuildMaster is stopped
2020-08-28 09:30:43+0000 [HTTP11ClientProtocol (TLSMemoryBIOProtocol),client] invalid login from unknown user 'ware-win81-release'
2020-08-28 09:30:43+0000 [HTTP11ClientProtocol (TLSMemoryBIOProtocol),client] Peer will receive following PB traceback:
2020-08-28 09:30:43+0000 [HTTP11ClientProtocol (TLSMemoryBIOProtocol),client] Unhandled Error
	Traceback (most recent call last):
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 460, in callback
	    self._startRunCallbacks(result)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 568, in _startRunCallbacks
	    self._runCallbacks()
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 1475, in gotResult
	    _inlineCallbacks(r, g, status)
	--- <exception caught here> ---
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
	    result = g.send(result)
	  File "/srv/buildbot/venv/lib/python3.8/site-packages/buildbot/pbmanager.py", line 217, in requestAvatarId
	    eventually(self.master.initLock.release)
	builtins.AttributeError: 'NoneType' object has no attribute 'initLock'