The buildbot UI can hang for long periods, particularly when a full/quick build is in progress and it is cancelled. The UI shouldn't hang and the cause needs to be found/fixed. Its suspected the console plugin API calls are already suboptimal and could do with improving which would help this. Also, we were scanning the poky-contrib repo with the git poller. There were large traces in the logs. When that was disabled the hanging problem seemed better so that may have been a contributing factor. Investigating other log messages may be relevant to addressing this.
The problem was due to the wiki plugin blocking the main loop in the server, those issues were fixed and the UI hangs were resolved.