Carpool7341 ah, didn't know it was roaming related. 802.11r relies on MAC address tables afaik, so it would be my conclusion that they become unresponsive when they're flooded with MAC addresses. (I can also just assume they're stored way longer than DHCP leases). At least it's solved.
I was just mentioning DHCP starvation because that is what I "did" to our company network when I hadn't noticed that my GOS phone was on "per connection" randomization. And our address pool is around 400 IPs for around 250 people (please don't ask who set it up like this lol)