Just had my 2018 Levo at my LBS today for the same problem! My mechanic told me it was the chain retention bracket not being adjusted properly! He has never heard of motor covers being a problem and basically laughed at me and told me to make an appointment so he could adjust the chain retention...
Well here's a update on my Shimano CN-HG901-11 chain. The chain has just over 1,000kms on it now and it is still under 0.50 on the chain gauge. This has not been treated like a princess like my KMC chain. It has been wiped clean and lubed after every third ride. I ride in strictly dry conditions...