This is quite interesting as I had something like this occur the other evening, just after I had installed my new Harmony Ultimate Hub.
I have a row of eight RF switches behind the TV (so I can individually turn/on off my devices).
Some of the switches stopped working.
I had to restart the plugin to regain contact - I suspect the plugin restart reboots the RFXtrx433.
I haven't had it since but will keep an eye open for it.