I get the same error below when trying to do different things in the Exchange 2013 EAC.  I've tried different browsers, OSs nothing seems to work.  Always in same areas I get that error.  Not all sections do it but some do.  I can do everything through powershell, but I really wanted EAC to do mailbox moves.  This is very frustrating, has anyone seen these critical errors before?

Hello,

I recommend you use server health and performance against your exchange server health.

Please check if there is any error in application log.

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Beefed up the VMs in my lab and the issue is no more.  Thanks.