Is True Image 2021 causing extreme slowdown on computers?

Very odd problem.  I'm seeing this over a period of a couple months. So far, affecting 5 computers.  I'm an IT service provider in my area, so all 5 computers are with customers that are businesses, managed by me, but are not related to each other.  

The problem is that the computer will be reported as being extremely unresponsive.  So slow that it's unusable.  The task manager resources/performance stats do not show the usual 100% CPU or drive utilization causes.  No single process or set of processes is spiking anything.  And yet, for example, trying to open Chrome or Adboe Reader could sit there for 5 or 10 minutes before it pops up. Once loaded, it usually behaves normally, unless an action you take in-app perhaps calls on some outside app or function, which then has a delay on it.  

But for example, I did a test copy of 10 GB of data from C: (an SSD), to D: (another SSD), and it went over at more than 500 MB/sec (Mega Bytes, not bits).  But just opening File Explorer had taken a long time.  

Another behavioral trait:  Right-click the desktop, no context menu comes up.   Alt-tab over to previously opened apps (alt-tab and actions like that are norma speed, mouse cursor movement also normal speed).  In my case, I did not yet click the mouse again, so technically the last mouse action was that right-click.  Minutes later, while in the other app, that desktop context menu pop-up finally shows up (overlaying onto the open app).  Clicking it, such as Display Settings produces the intended result.  

Clicking the start menu, doesn't open.  But mouse-overs are real time, you can see icons highlight or color-shift, etc.  

In these situations, the only solution has been to wipe the machine and install from scratch.  No amount of uninstalling, update rollbacks, etc. have worked.  Though, in all cases to date, the option has not been there to put extensive time into uninstalling things. 

These are very generic business computers (Dell, HP, and Lenovo), and all are solid hardware so the issue is not that. 

However, one common thing to every machine is that they all run Acronis.  Most are True Image 2021.  One is Cyber Protect.  Interestingly, the Cyber Protect one does not have auto-update enabled for the Acronis agent, and yet the problem cropped up on that machine anyway.  

The other commonality to all machines affected is they all have Symantec Endpoint Security on them (enterprise edition).  However, I have dozens of other systems in many environments all uses SES, and this product with its enterprise customer base is not going to have this kind of issue, whereas consumer antivirus frequently sees complaints like this.  However, maybe the combination of SES and Acronis is the problem, or just Acronis on its own.  Certainly I suspect the new built-in antivirus/protection features in Acronis can easily be the issue, becuase A:  it's new, so there will be problems for sure, whether we hear about them or they quietly get fixed in patching, who knows.  B:  the old idea that two antivirus on one computer still comes to mind, whether or not the vendor claims coexistence is possible.  I don't seem to see a way to fully disable the Acronis non-backup features.  They're clearing pushing hard for adoption of this.  

I finally have a computer here that I'm authorized to take my time with, and wipe clean if need be as well.  So I will remove Acronis and with any luck it's a direct result and the system will be normal.  

However one last point.  On affected computers, the longer than stay up, the less this problem happens.  So if I reboot, the problem is very fresh and nothing opens, even the login to the desktop takes a long while.  If I leave the box running for some hours, I can open things more quickly, though in some ways the problem is still evident.  But on a reboot, it all comes back.  

My guess:  Acronis has a bug that's extremely hard to isolate and reproduce.  Take an existing/affected machine, wipe it, reinstall everything to the same patch levels as before, even with Acronis, and the problem is gone.  

Ugh, computers!