This was a lot simpler than I expected (#16230)

code/modules/mob/living/silicon/robot/drone/drone.dm

@@ -300,11 +300,7 @@
 	if(!player)
 		return
 
-	if(player.mob?.mind)
-		player.mob.mind.transfer_to(src)
-		player.mob.mind.assigned_role = "Drone"
-	else
-		ckey = player.ckey
+	ckey = player.ckey
 
 	to_chat(src, "<b>Systems rebooted</b>. Loading base pattern maintenance protocol... <b>loaded</b>.")
 	full_law_reset()

code/modules/mob/living/silicon/robot/drone/drone_manufacturer.dm

@@ -37,7 +37,7 @@
 
 	icon_state = "drone_fab_active"
 	var/elapsed = world.time - time_last_drone
-	drone_progress = round((elapsed / config.drone_build_time) * 100)
+	drone_progress = clamp(round((elapsed / config.drone_build_time) * 100), 0, 100)
 
 	if(drone_progress >= 100)
 		visible_message("[src] voices a strident beep, indicating a drone chassis is prepared.")