NTWS behaving strangely

I’m currently experiencing something very mysterious with a larger NTWS app I’ve developed.
Several of my forms are behaving strangely. When I press “Insert” in the browser, the form opens as it should. Then I press “Cancel”.
When I repeat this exercise, the process starts to take longer and longer. When I get to the fourth time, it takes several seconds to open the form - the fifth time over 10 seconds.
Chrome and Edge go crazy in processor usage - up to 100%.
This happens in several forms. Other smaller forms work fine.
My first thought was Antivirus but I’ve moved the app to another PC and it gives the same result.
The thread number never goes above 5 so I don’t think it’s due to a hanging thread.
The only thing I can think of that I’ve changed is updating NTWS from 14.28 to 14.29.

UPDATE: Now I’ve tried downgrading to 14.28 but it makes no difference. So it must be something I’ve done…

I’m a bit lost. Any ideas?

Regards Niels

Are you running the app in a browser? If so, can you enable debugging in the browser (F12) and see if the delay is evident in any of the information received by the browser?

A suggestion from Bruce helped me in the right direction. A self-made template on my popup forms didn’t clean up after itself.
Thanks.