I know you don't want to go through and edit all your clickitem instances... but something to try at least as a POC, right before one of your "clickitem" calls, also make a call for the same object to execute the method/action "scrollIntoView" with a parameter set to "true". It's possible that the upgrade to Windows 10, with your application (especially if the component is inside a frame inside the page), that TestComplete's "auto scroll" capability may be hampered. I've seen this happen in our own systems. Explicitly calling "scrollIntoView" as I mentioned will alleviate that problem.
At least give it a try in one instance to see if it resolves the problem.