Hi, thought I'd jump in as we went through something similar recently. ITA with Vicki that it does sound like an UT nap, so pushing the A will more than likely resolve the issue.
However, what I've found is that DD has suddenly dropped the amount of sleep she needs in total. At first I thought she was OT but actually it seems like she's needing 30mins less sleep a day all of a sudden! You may find that a 2-hr nap will suffice now xx