MAX BR1 Mini not serving IP addresses reliably

My Max BR1 mini has been reliable serving IP addresses, incl some reserved IP addresses, but after a reconfiguration (addition of routerBOARD to add new devices), is proving problematic. Have had to revert to fixed IP addresses, however on power up even these take time to gain network access.

Network hardware consists of 1 x BR1, 1 x Mikrotik routerBOARD in Bridge mode, and a generic 12 port Switch.

I have factory reset, been through all settings, has me stumped.

Any thoughts/ideas gratefully received.

Sounds like a network loop, or the bridge mode routerBoard is causing ARP collisions.