Nap transition HELP!

I’ve been trying to get my son (16mos) down to one nap for the last few weeks he was going down for his 10am nap great, napping until close to 12, then fought like heck to nap at 2 so I pushed it to 3 then he was fighting that and falling asleep at 4 and too close to bed time which is 730. So I’ve tried to push his nap 15 mins each day and it’s been going ok, however every day around 930 am he gets SO SLEEPY. If I have him in the carrier or out for a walk in the stroller, he falls asleep. Then fights his nap until 1-130 and will nap until 230/3. I’m just trying to figure out if this is normal and how to help him avoid the cat nap at 930 some days 😖 my oldest switched early to one nap and was a solid napper from 12-3. I’m feeling at a loss