KB5002701 contains unsigned executable

One possibility that has been suggested is that there is a hanging instance of Access that prevents it from running. Given that rolling back the update resolves the problem, that seems less likely, but needs to be eliminated as a potential source. Also, the fact that it's occurring on multiple workstations. 
Nonetheless, we'd like to eliminate potential contributors. 

Also, I just picked up on a subtlety in the way you described the problem. You refer to the "MSAccess executable". Some people refer to an accdE that way. But perhaps that's not what you meant? To be sure we're on the same page, and that you didn't mean something else, can you confirm that as well?