Appreciate the responses received, did a test last night connected to router via wired and it knocks that out too.
To me it’s odd that devices which have reservations already get impacted also, can understand that those without would be impacted.
there are checks preventing you from reserving more than one ip per device, so why kill the whole network?
Also, the IP address being reserved has already been allocated to the device via dhcp, I’m just adding it to the table as fixed. If I was giving new then yes, I agree it would flush and re-allocate to pool but again, why disconnect everything?