I'm assuming your just lightly covering the screen with grass clippings or ground duff like what's done in the pipe dream set and using the screen to hold it up so it looks like a flat level place to step? If this is the case my question would be how do you know they are accidentally moving the screen when they step on the jaws instead of knowing something is up and intentionally moving the screen? Similar action as when u are using dirt and have a digger. If it's the latter and they are on to u, the rubber band isn't going to fix the problem. I've tried the pipe dream style of covering traps and understand in certain weather conditions it's a good option, but here in my area it will sure enough decrease your catch rate compared to using dirt and adequately freeze proofing your set for the given conditions. But I might not be understanding your situation and problem so this might not apply to the op
Iv delt with racoon diggers and dont seem the same. What appears is paw goes straight down on jaw and couple toes fall through ID of trap. Dont know if screen moving or toes inside trap never hitting solid ground spook then. That is usually all I see is one jaw step and center of screen showing because less material there. I agree hard to beat good wax dirt set but I need to work this out. And also going to start placing set deeper and adding more peat, grass clippings. Also loose much eye appeal with this set not seeing dough out dirt. Makes for locating set difficult.