Hi Chris as a starter try this. I have Orbi Mesh and a Oneplus 9 pro and they work great.
With a oneplus 6 I would make sure you turn off app optimisation to stop Roon being swapped out of memory.
Also try turning the windows firewall off
There’s also an entry in the network kb article about a setting change on Orbi, so check that out as well
I hope this helps.