The sear engagement on the right barrel needs to be adjusted. You need to place it in the hands of a competent gunmaker. GSI, the Merkel importer, has a qualified gunmaker on the premises. Try them first. They know Merkels quite well. They should fix it for free if it is under warranty, and may do so anyway since it is a safety issue.

You could also consider J.J. Perodeau at Champlin Arms for repair. This is a simple and relatively inexpensive repair, but it's not something your local gunsmith can fix.

Curl

P.S. I have had this same problem with two very nice sidelocks. The fix is not a problem.