In my opinion, NiCads were the bigget scam to ever hit the market. Because of memory effect and the tendency to grow internal "whiskers" over time, they have a very limited lifetime compared to NIMH. Manufacturers loved to put the in their products like power tools because they knew it would create an endless market for the battery replacements (at very hefty premiums). When they fail, it is pretty abrupt from my experience.

You could spend time and money trying to "cycle" the lfe back into them, but I strongly recommend switching to NIMH, especially for the receiver where reliability is critical!

Art