Hi, It looks like a memory error which could be from the transceiver change. It is possible that the Unifi one isn’t compatible and was causing an issue. You could try updating the firmware on the switch when you have a maintenance window.
we have 3 n3048 stacked in a rack, this is our backbone. one of the 3 had ftlx8571d3bcl gbic that connected fiber to another dell switch across the street, same model gbic. that dell switch across the street was going bad, so we were replacing it with a unifi switch, and it did not seem to like the gbic, so we replaced both with unifi 1 GB gbic. everything looked good for couple of minutes, the unifi came up, but then it looked like the unifi went offline. then someone came running to tell me the entire network was down. since the only thing I did was replace that gbic, i put the old one back in place. within couple of minutes the network came back up. connection to across the street still offline. only error I found on the dell switches in the rack was: _soc_mem_array_sbusdma_read: FP_COUNTER_TABLE.ipipe0 failed(NAK) could this error have been caused by the replacement gbic, or is it a coincidence?  
N3048 error when replacing gbic