I would take "process of elimination" approach to this:

1. COMPLETELY disable A/V on all related servers for a short test period and test (APP Server to start)

2. Install (even temporarily) Workstation Setup on DB Server (test communications between DB Server and other computers).  If this runs well, you have a communications issue - network, antivirus,  firewall etc 

3. Ensure there are no outdated entries in Customization Directories (Administrative Services)

Good luck!

Shane

You did describe issues with screens opening slowly but there is a hotfix for that:

https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=89045&sliceId=1&cmd=displayKC&dialogID=559136&docType=kc&isLoadPublishedVer=&stateId=559138&docTypeID=DT_Article&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl

Make sure that the VM hosts are not using dynamic ram allocation.

Since you can reproduce in sample data it would be a good time to run rvSpy, dbSpy and run a database trace to get some metrics.

Check for windows defender as well as other anti-virus software as this is a real killer and is loaded automatically
at a client recently the IT dept excluded the USERDATA directory where the user profiles are held on the terminal server from defender and virus scanners and it made a huge difference

Hello, I am exactly in the same situation, I have an infrastructure equal to yours. I would like to know if you found the root cause of the problem

Hello, I am exactly in the same situation, I have an infrastructure equal to yours. I would like to know if you found the root cause of the problem

Are any of your VM hosts overallocated?

How are the workstations and terminal server installed? Wssetup or full workstation installs?

"58GB main company Database ( log, temp and main database split over 3 drives)"
Don't think this matters on a VM. The whole purpose of putting log, temp, and main database on different drives is to spread the read/write load over different physical I/O.