Shoulder button membrane switch won't stay together

Hi guys. First time posting so sorry if I'm stupid and didn't attatch the image properly.

I took apart my controller cause r1 wouldn't spring back and discovered the pad fell through the slot of the membrane. (right one in the image, left is intact) I tried putting it back up but it just falls through again when pressed. I've never dealt with membrane switches before so please tell me if i'm missing somthing.

I found a post here on the forum where someone else had the same sholder button problem and a recommendation given was to order new membrane and replace it. But op hadn't opened it yet and didn't return with updates so i thought i should ask if i can fix it on the spot first before ordering, just to save myself the shipping time.

Thanks in advace