I'm pretty sure that Strawberry sorts by metadata. A song needs a track number, independent of the file name. The suggestion of renaming files numerically is a good idea. Organizing your album folders alphabetically, by song name, runs counter to the way albums are presented -- which is numerically, by track number.

Right click on a song and select "Edit track information". There should be a number in the "Track" field at the right. Don't change anything yet, until you figure out the root of your problem, but if there is no number, that might be of concern.

Hope that helps.