This was never previously a problem. So I suspect something has gone wrong at Foursquare’s end (which is where the searches are done).
It might be worth searching Foursquare’s forum (if they have one?) to see if others are having this problem.
Foursquare recently launched a new v3 version of their API and database. But Arc still uses the v2 API and database, due to various issues with the v3 database and API (missing places, weird search results, etc). I wonder if v2 is getting neglected. Though this appears to be a regression, which would mean they’re still making changes to v2. Hmm.