MR52 users' experience

I recently installed openwrt on an Meraki MR52. I had some problems with the 5G radio which I posted here.
Thinking I'd resolved it, I marked the thread as solved and put the AP away for later use.
Now I come to use it I'm finding 5g connectivity is not working. Client devices ofetn cannot even see the the 5g BSSID and, when they do, either cannot connect or connect very briefly and disconnect. They don't even seem to stay connected sufficiently to make complete DHCP.
I wondered if any other MR52 users experienced issues with 5g radio? I'm powering it the same as my MR42, that is is via the 12VDC input with which the MR42 works well. I have tried PoE but the MR52 behaves the same albeit seeming to run hotter.