lost signal keyboard not working but mouse does.

has ayone noticed this, I have 6 of these and they all have does this, the original one lasted me a few years of pretty heavy use, the second was garbage, the third lasted most of the rest had short lives.. if you squeeze the back the keyboard ill flash a few times and it will work again I tried new batteries i tried a peice of credit card to hold battery against tabs tighter. cleaned battery terminals and pins, now if i charge it and use it , this doesnt happen., which is why I purchased a couple batteries. I havent taken it apart to clean the keys, it doesnt seem related. So Im asking, has anyone had this happen and will a teardown and cleaning stop it?