You don't need to restart when making the changes from the interface - only if you're changing the batch file etc.

To prove this, drop your gpu clock to something very low and watch what happens.

I only ever tweak my miners via the menus then, once i find the sweet spot, i lock it in with the batch file.

Doesn't answer your question as to why it drops though. Do you have --auto-gpu/fan/mem/temp set in the config?