I have dealt with this on one of my E-M1 bodies. This really only seems to be an E-M1 issue. The rear dial most commonly for some reason. It just stops registering every click. I am not sure if its an encoder wheel or what exactly, but once they fixed it, it never came back. It happened on my first E-M1 body which was a purchase closer to the original release time. I have a later body that has not experienced this. I can dig through my files and pull up the repair ticket to see if they actually listed what part was replaced if you are interested.
If the problem re-occurs, the repair should be warrantied. Olympus actually has a couple contracted places where repairs get done, and not all have the best reputation. Perhaps it was not done correctly the first time on some of those cases. Would not surprise me unfortunately. In the larger picture, Olympus has been very responsive to repair issues, and to correcting issues that the repair techs for a certain place were not able to take care of properly. I am happy with them, but I would much prefer a system that models Canon CPS program, even at cost.