Unexpected disconnection in a Zana map after doing tower minigame

This was a real feel-bad moment. I had 3 uniques and a purple item I hadn't seen before on the ground (using neversink semi-strict filter)

I was in a zana map which had the "killing enemies close together may call enemies from beyond" mod. Immediately after finishing the tower defense a beyond mob spawned behind me with a 2H sword and swung at my back.

At the split-second that the sword would have connected with my character I had an unexpected disconnection error and was booted to login screen. I was able to re-log immediately but was obviously kicked from the map and all my loot.

I have a feeling this may have been triggered due to some combination of factors of the map being cleared, being in a Zana map and a beyond monster being spawned just as I finished a tower defense.

Please let me know if you need any logs to investigate this. FYI my connection is rock solid, this is the first time I've had this disconnect message in memory.