Clients are ultimately the decision maker on roaming. And each client type has different wireless adapters and drivers/baked in roaming behaviors. It's the most challenging part about wireless design & troubleshooting even 25+ years into enterprise 802.11 Wi-Fi.
That said when clients bounce around a lot between APs that often indicates an AP RF plan that needs some optimization. As mentioned above you could try disabling client load balancing (if you have that enabled now). Beyond that I would also review how your RF profiles are configured. In high density environments you often need to massage the RF profiles for things like lowering the maximum transmit power to create better/more appropriate RF cells and cell overlaps between APs.
In your deployment are the MR53s and MR55s mixed together per floor? Or, do the models align to specific floors? Mixing hardware generations like that, Wi-Fi 5 (ac) and 6 (ax), can introduce some extra challenges for clients. A Wi-Fi 6 capable client likely is programmed to prefer 802.11ax first and with certain signal strength cutoffs. A client like this could encounter roaming issues when it sees some 802.11ax APs while others are 802.11ac.
Every deployment is unique and therefore there's no one single answer for them all. As a start I would review the info in the High Density Deployment doc and see if any of those suggestions help your client roaming.
