Strange twist using Timer Recording

Over the last 6 months, every weekend, I have been using the timer-recording option to record two 23-hour streams of audio for research purposes. I have been saving the tracks to a memory stick and on Monday there is still room on the stick for more recording. After I am done with the tracks, I delete them and use View/History to clear out “Space used”.

Well, that is until last week.

Now when I set the first timer, it reports that there may not be enough room to save the file and the stick becomes totally full. I have reformatted the stick but that did not make a difference.

Any thoughts on this?