Casio AWR-320 problems

My second Casio ARW-320 has a problem. After 4 minutes the analogue module stops. 
The problem is in one of the small plastic wheels. It has a broken tooth. I've tried to put the tooth in the correct place but it was broken, so right now the ARW has a missing tooth but works :)
I'm checking the accuracy of the watch. With a missing tooth seems clear that it will loose some time. The first 2 hours it loose 2 minutes and 40 seconds, a little bit more than 30 minutes per day. It is not a good accuracy, but it works more than 4 minutes ;)
I will try to look for an old destroyed ARW-320 in order to get a good wheel.