SPOILERS BELOW
Oof, that definitely sounds super frustrating, sorry about that! The trouble with text adventures games is always figuring out what commands the game likes and which ones they don't.
For WGDITD, it functions with VERB-NOUN commands, so that's probably why using the prepositions (use ITEM on OTHER ITEM) aren't working. Try typing CLEAN SYMBOLS, ERASE SYMBOLS, or WIPE SYMBOLS and see if that helps!
Thanks for bringing this to my attention! I'll be sure to add in those commands in an update so other people don't get stuck in the same place!