| I always wondered if my unit was acting normally, and I could never find anything that referenced the 'issue' I was having; When my RC-50 would fill up, I would back up what I wanted to my computer and then clear the RC out... then when I fired back up, all the patches would be empty, but I would still only have a minute or two of recording time available.
Its been a bit since I've been through the process, but basically you have to 'initialize' (iirc) each patch that has been recorded on, even if there appears to be nothing in it. The initialization clears it out, returns the recording time, and resets all patch settings to default configuration-- kind a pain, because I would have different settings in each patch (ie mono vs stereo) and would have to set it all back up after 'initializing'.
If you have used many patches, initializing each one individually can take a while, so I found the 'factory reset' to be the best option- after reseting, the RC-50 is in stock configuration with the full 24/48min recording time. You can find the 'Factory reset' instructions on page 95 of the manual, and its a quick and easy process consisting of only a few simple steps.. Hope this helps! | 
