I dunno if you've asked on Discord
but its been reported/added to try and alleviate/be a clearer sign of AI pathing issues
If you're getting more than one customer, check around the map, see if there some kinda AI/NPC issue brewing near the Bridge, or the two Exit portals (left and right of the shop)
If there is, good, coming near it and helping clear it up should help the issue
if not, Switching free mode/shop mode, and saving/resloading, will help by despawning npcs, but it may not change the overall situation.
we still, or rather, I still, which is rather unimportant, seen a reasoning to explain the issue.
it could just be overzealous codework that was introduced in the dev build that is reacting to even the slightest NPC issue.