Are you sure that you don't save your patterns always on the same slot number ?
When you save your pattern on the [M] screen (memory screen) you have to select its slot number before,
place cursor on the slot number, it will be highlighted then with L/R pad select its number, after that you can save your pattern, it works the same for song sav/load,
normally if you choosed a name for your pattern you must see it facing its slot number like :
00:PTN0, 01:PTN1, 02:PTN2 etc...
but i have to say that it seems to be bugging, i've seen a song name in place of pattern name, sometimes no name at all or, the name of another pattern and in this case the content of the pattern itself as changed too, for example P00 and P05 were named both test 5 and in the [T] screen there were identical when i tried to edit them
When it wasn't bugging i have noticed that, in [S] screen (song screen) if you change the number of the pattern in a slot by an precedently created (and saved i presume) pattern name, it loads it directly (so why is there a pattern load function ?!).
I have not experimented other crashes and freezes but, i got another bug, and so does HIA, when you hit Select+Start for playing the song, the last step of each pattern play with a slow cut (i dunno how to describe it better) and it results in making each pattern out of sync, very very frustrating