Hi,
I am using the same clas in my program too. However, it is a small program with fews forms. It work fine. Back to your question, I used to face it before. But, seem you said that all of them all the same, let try to include one of the form to your large program and see it work as expected or not.

And, how many forms opened at the same time? As we know, the timer is added to every form. What I did to prevent too many timer, I add it to _SCREEN instead.

HTH