I think it sounds like an UT/OT loop....I would go back to a 2h30 A time consistently, I suspect after a short first A and good first nap (occasionally needed as a catch-up) she was UT and therefore resisted the next one. And then got OT hence back to 30 mins. DD used to do that, we had more luck if she wasn't asleep quickly in getting her up, playing for 15 more mins then putting her back down. Left to her own devices she would just keep playing and never settle. Then end up OT.
Hang in there x