RDP process (mstsc.exe) is freezing local workstations by maxing out the CPU

We are unable to find a common cause of these CPUs maxing out.  Seemingly random users utilizing multiple and single Remote Desktop instances, some have been idle and some lock up while working.  Once ending task/process, CPU returns to normal and the connection can be re-established with no issues.  Until it happens again.

Servers are hosted in AWS using EC2 instance.  
15+/- concurrent sessions on server at once.
Applications vary but mostly DocStar, Chrome and Outlook.
All workstations are on latest WIn10 Pro version and updates are current.
Sophos Endpoing on server and workstations

We've checked system/application logs on both server and workstation but no warnings, errors or log entries appear at the time of freeze up.
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Neadom TuckerAsked:
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David Johnson, CD, MVPRetiredCommented:
There are several tiers of EC2 it could be a multitude of problems
In my lab the cpu is 0 for mstsc memory is <23K
Neadom TuckerAuthor Commented:
Are there any specs or logs I can provide to narrow this down? We have worked with AWS and they've assured us the issue is not on the EC2 instances since the CPU issue manifests itself on the local workstations.
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