OK, I hope I'm not too late to post a reply on this topic. If you want a Flexaret shutter repaired you could get in touch with Cupog (search on ebay for him). He does repairs and cleaning of Flexarets. If you are handy you could get the shutter of the body and send only the shutter but maybe it's a good idea to get the whole camera checked. Luckily, the Flexaret IV isn't the most complicated of the Flexaret line.
The only con is that cupog is located in Slovakia while you are in the US which makes postage maybe a little expensive. Another option is to find someone who is familiar with older shutters, Meopta used German made standard shutters on the Flexaret IV (later on they changed to Metax shutter produced in Czechoslovakia itself) . But you could only use this service if you are certain that all other things work like they should (and I'm speaking about the film counter/transport in particular).