I found that updating from v2.0.6 to 2.5.7 there is an "unknown artist" empty selection sorted as first. Inside, there isn't any album or track.
There is also a "Various Artists" that also seems to skip alphabet name sorting.
When I reset sorting (sort by name (desc) and by name again), both are correctly sorted (although the empty unknown artist remains). When closing and opening the app again, it sorts wrongly like the first time.
On the songs sorting, there are songs with spanish sings "¿" and "¡", that are interpreted separately from the rest of "#" list sorting (this list includes numbers, parenthesis, etc. title songs). They obviously should be together.
See pics below:
