Not all user tracks are converted to midi files

[Lernni]

My YAMAHA PSR E413 can store 5 user files each with 5 user tracks. A maximum of 25 midi files should be converted, but only 21 could be restored. Interestingly, there is a pattern visible, when looking at the missing user tracks:

In the first 4 user files, always the first user track is missing. In the last user file, the first two user tracks are switched.