regiond on the second node has the corresponding traceback, and just before it it seems that there were disconnection from the rackd:

2022-03-18 12:05:26 maasserver.rpc.regionservice: [info] Rack controller 'gbmc77' disconnected.
2022-03-18 12:05:26 RegionServer,1,::ffff:10.245.222.214: [info] RegionServer connection lost (HOST:IPv6Address(type='TCP', host='::ffff:10.245.222.213', port=5250, flowInfo=0, scopeID=0) PEER:IPv6Address(type='TCP', host='::ffff:10.245.222.214', port=40408, flowInfo=0, scopeID=0))
2022-03-18 12:05:26 maasserver.rpc.regionservice: [info] Rack controller 'gbmc77' disconnected.
2022-03-18 12:05:26 RegionServer,1,::ffff:10.245.222.214: [info] RegionServer connection lost (HOST:IPv6Address(type='TCP', host='::ffff:10.245.222.213', port=5251, flowInfo=0, scopeID=0) PEER:IPv6Address(type='TCP', host='::ffff:10.245.222.214', port=40690, flowInfo=0, scopeID=0))
2022-03-18 12:05:26 maasserver.rpc.regionservice: [info] Rack controller 'gbmc77' disconnected.
2022-03-18 12:05:26 RegionServer,1,::ffff:192.168.33.158: [info] RegionServer connection lost (HOST:IPv6Address(type='TCP', host='::ffff:192.168.33.157', port=5253, flowInfo=0, scopeID=0) PEER:IPv6Address(type='TCP', host='::ffff:192.168.33.158', port=40514, flowInfo=0, scopeID=0))
2022-03-18 12:05:26 maasserver.rpc.regionservice: [info] Rack controller 'gbmc77' disconnected.
2022-03-18 12:05:26 RegionServer,1,::ffff:10.246.64.7: [info] RegionServer connection lost (HOST:IPv6Address(type='TCP', host='::ffff:10.246.64.6', port=5252, flowInfo=0, scopeID=0) PEER:IPv6Address(type='TCP', host='::ffff:10.246.64.7', port=48690, flowInfo=0, scopeID=0))
2022-03-18 12:05:26 maasserver: [error] ################################ Exception: Connection was closed cleanly. ################################
2022-03-18 12:05:26 maasserver: [error] Traceback (most recent call last):
  File "/snap/maas/18199/usr/lib/python3/dist-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/snap/maas/18199/lib/python3.8/site-packages/maasserver/utils/views.py", line 284, in view_atomic_with_post_commit_savepoint
    return view_atomic(*args, **kwargs)
  File "/usr/lib/python3.8/contextlib.py", line 75, in inner
    return func(*args, **kwds)
  File "/snap/maas/18199/lib/python3.8/site-packages/maasserver/api/support.py", line 56, in __call__
    response = super().__call__(request, *args, **kwargs)
  File "/snap/maas/18199/usr/lib/python3/dist-packages/django/views/decorators/vary.py", line 20, in inner_func
    response = func(*args, **kwargs)
  File "/snap/maas/18199/usr/lib/python3.8/dist-packages/piston3/resource.py", line 197, in __call__
    result = self.error_handler(e, request, meth, em_format)
  File "/snap/maas/18199/usr/lib/python3.8/dist-packages/piston3/resource.py", line 195, in __call__
    result = meth(request, *args, **kwargs)
  File "/snap/maas/18199/lib/python3.8/site-packages/maasserver/api/support.py", line 308, in dispatch
    return function(self, request, *args, **kwargs)
  File "/snap/maas/18199/lib/python3.8/site-packages/maasserver/api/support.py", line 158, in wrapper
    return func(self, request, *args, **kwargs)
  File "/snap/maas/18199/lib/python3.8/site-packages/maasserver/api/pods.py", line 341, in compose
    machine = form.compose()
  File "/snap/maas/18199/lib/python3.8/site-packages/maasserver/forms/pods.py", line 731, in compose
    result = wrap_compose_machine(
  File "/snap/maas/18199/usr/lib/python3/dist-packages/crochet/_eventloop.py", line 231, in wait
    result.raiseException()
  File "/snap/maas/18199/usr/lib/python3/dist-packages/twisted/python/failure.py", line 467, in raiseException
    raise self.value.with_traceback(self.tb)
twisted.internet.error.ConnectionDone: Connection was closed cleanly.


which isn't unfortunately very informative