Maybe you are (or have been in the past, read on) pestered by a UDF formatted device. Can be your NAS ...
On a side note because nobody will understand, including me, is that :
or you show a different source in Explorer from what you loaded into XXHighEnd;
or this is FLAC and the Track Numbers are in there.
The latter is sort (pun) of what you implied, although you never told it was FLAC. So it is my guess it is and it contributes to the confusion. Now, let's see in here for an example of similar (not the same !) :
Wrong order in Playlist Area ?
There are more topics about the phenomenon, but the one behind the link above makes it quite clear (ahum). Otherwise search the forum for UDF and user PeterSt and you'll find a few more, with the notice that this is all solved by now.
Not yours ...
The problem summarized (technically)
When a folder is scanned for its contents, the result is *always* brought forward by the sequence of creation. Regarding this you may just as well think date-time although often the time (minute) is the same. So it really is so that physically it is written to the table of contents in the sequence all was created.
There is no way around this.
It is read back in the sequence which is stored in the table of contents.
There is no way around this either.
Notice that I am talking about the programming functionality which "enumerates" the contents of a folder. This would work the same as when you start explorer for a folder and you never sorted it exlicitly on anything. So yes, you can sort explicitly, but the programming facility which "enumerates" can not. We can sort afterwards though, just like in Explorer.
But we don't want that ...
Things would go bad when two albums are in the Playlist and first we'd have track 01 of the one, then track 01 of the other, then 02 of the one, then 02 of the other, etc.
The problem summarized (functionally)
Where it goes wrong is at some "source point". Thus, if you are "capable" of having a wrong sequence - and which is possible by leaving out the track numbers and now sort it on Name (which is alphabetically) and *then* copy it to elsewhere, the copying goes by alphabeth sequence and at the other side it ends up in that sequence written. And now you can add track numbers what you want, you will not be able to let change the enumerating program facilities the sequence of coughing up. It's like the table of contents of a book being mixed up and writing the chapter numbers with pen next to it (at the left side) won't change the printing of the page; It is too late.
When you took (or want to take) the effort of adding the track numbers to it anyway, then sort it on alphabetical sequence (now it looks all OK) and from there copy it one time. Now the copying process will be in the proper sequence and at the other end the table of contents will be in the proper sequence as well.
And now it is normally usable.
And solve a bug ?
Nah, not a bug. But what you showed is that XXHighEnd *is* able to come up with the Track Number, which is stored internally in the FLAC. So yes, I know I made that, ever back. Now :
If you look at the other topics (apply mentioned search) then you see that more of such anomalies could be solved, like the HD Tracks fine (stupid) sequence of 1,2,3,4 instead of 01, 02, 03, 04 which all is fine when less than 10 tracks. But when more (like 12) it is going to be 1,10,11,12,2,3,4. IOW, there sure *is* explicit sorting in there, but I guess that happens before the track numbers are dug up from the FLAC header data. So that is not convenient.
And if it isn't clear by now : in such a situation the tracks are - without track number - in proper sequence because they were written (!) in proper sequence by the ripping software (which just starts at the beginning of a CD).
All together it is error upon error upon error which lets this fail.
I can look into it, but expect it not to be solved fast (has to wait until the next version (2.06)).
PS: Please explicitly confirm that the track numbers you showed in XXHighEnd are NOT in the file names and that they have to come from FLAC. If you are not 100% sure what I'm asking, please say so.