I happen to be a beta tester for Aspire. A few years ago, one of the other testers knew of several people experiencing what you are. Several other Mach3 users did not experience the problem, and claimed the issue was caused by CV settings. I just went back and read through the messages, and no specific settings were mentioned to eliminate the problem, and the original poster never followed up with any resolution.
So, unfortunately, I don't have any answer on how to eliminate it. I never use tabs, so haven't come across this issue.