Cannot confirm.
Check contents of skins folder in BS.Player's installation folder.
Normally you will find
one folder named "Base" there and a number of .bsz-"files".
(Actually those .bsz "files" are archives containing similar files as those in base-folder).
I suspect your Skins-folder contains more folders than one and that the names of these folders correspond with the names of the .bsz-files.
If so: delete all "same-name"-folders with their contents
except Base-folder. Then also delete the Base.bsz-file.
(Maybe you have been experimenting a bit?
Control bar at the top in full screen?)