Naps are wonky?

My son has been on 2 naps for a month and he was doing so well. Each nap was at least 1-1.5 hours long. Now all of a sudden he's waking up after 30 mins crying. Usually during his second nap but it has happened during his first. What is going on? If I leave him for the full hour it does not help and he won't go back to sleep. He is clearly upset. I've tried feeding him a bottle closer to naps and offering tylenol on bad teething days. I'm pretty sure it's teeth... but is it possible he needs one nap now? I always thought they were ready to transition to fewer naps if bedtime was getting pushed too late.