Nope, it's really just the wrong mapping... it's the same for Fantasies/Mania and for Dreams too btw, haven't tested Illusions yet... I wonder why it hasn't been addressed by the GOG team yet.
They have a customized DosBox mapper file in each folder (mapper.txt) which seems to not
have the Shift keys mapped properly. Deleting those mapper.txt files (in all the folders where
necessary) will solve the problem. If you're playing Dreams, delete it in "dream1_tables" and
"dream2_tables" folders, if you're playing Fantasies/Mania - in the "fantasies_tables" folder, and if you're playing Illusions - in the "illusions_tables" folder. ;)
Oddly the game works just fine in Fantasties. But not Dreams. (Haven't tried the others yet)
SHIFT keys were remapped on purpose, to avoid problems with Windows Sticky Keys function popping up. Keys can be remapped inside the game, so it's not really a bug.
I remapped them in-game. Still does nothing.
Edit: Nevermind I was trying to test the flippers before launching the ball (Like fantasties allows, and every other pinball game on the planet)