I have a Wii and two controllers. In the last few months the controllers lose the connection to the Wii rather often. It's bad enough that we cannot play Mario Kart any more (because one player gets disconnected every few seconds). If I play Super Mario All Stars on my own, it disconnects less often, but when it does, it's always in a jump (which then ends, catastrophically for poor Mario).
I tried replacing the battery sets, thinking that maybe the rechargeable battery sets had issues. But that didn't work.
Nothing in the setup or the room has changed. Connectivity was perfect before this started with rarely a disconnection happening.
I checked for bluetooth devices in the vicinity but bluetooth is switched off in all computers around.