HELP!! Stuck calls in Queue

[Dub]

I'm currently having an issue that I don't understand and can't seem to fix. Basically I have 3 main queues (a, b, c) with several agents. Most agents are part of 2 of the queues and some of them part of all three. The problem that i'm experiencing is that when the calls come in it seems that sometimes the calls seems to get stuck in either the a or b queue when agents are available but the calls do not ring their extensions, while the other 2 queues are working fine. This goes on for a while but only happens on either queue 1 or 2. I tried rebooting the server, restarted queuemetrics and asterisk and nothing. The problem just seems to fix itself after a while then comes back. If you guys can help it would be great.

[QueueMetrics]

This is of course an Asterisk issue, so it is not related to QM - QM has no say on how calls are distributed. 

Still I understand it is a major PITA. This is what I would do:
- turn on maximum verbosityu in Asterisk logging
- wait for the problem to happen and write down the time and ID of a call
- try and look back on the log for any suspicious entries

Do you have autofill enabled? if not, it may be worth trying.