until the time you began having problems again what applications or utilities have you used for the computer(s).

Often various utilities will locate "something suspicious" and offer to "fix" it an unless you actually know what is getting "fixed" the fix will result in problems that are seemingly unrelated.

Besides listing the utilities such as registry cleaners, anit-malware apps, duiplicate file removers, uninstallers, etc. for us to see there is something you might be able to do and that is to perform a system restore back to a date before the problem.