TileSet not using the updated sprite

This "bug" has been annoying me for a long time now, many, many months (maybe over a year).

I have a TileSet, which has a sprite associated with it, and setting tiles to each cell works fine throughout the game, no problem.
BUT, if I make changes to the graphic in PhotoShop or Aseprite, save it to disk, and then load the new sprite into GM2 to replace the graphic that it was using, the changes made almost always are not visible in the game...

TileSet not using the updated sprite