Highlighting irregular nouns and verbs?
Just a thought-- I keep repeating the same mistakes (in Italian) with the same irregular nouns and verbs-- would it be possible to highlight (or italicize, or change the color of, etc.) the words that don't follow the "normal" usage?
For instance, in Italian, if the word "qualche" (some, or, a few) appears then you don't use a plural noun after it. So you would write/ say "qualche ora", instead of "qualche ore", for "a few hours".
Or, masculine/ feminine gender nouns that don't conform: "il diploma", "la prigione"-- you could highlight the words diploma and prigione IF/ WHEN the article doesn't appear with the noun.
A little visual hint to tell us that a word is just a bit out of the ordinary would make things easier but I would also then get used to seeing certain words highlighted and that would certainly aid the memory.
Just one different color required. If it isn't a "normal" usage, it is colored differently.