If you grind the plastic adaptor, you need to grind it 12 times. ( there are 6 different sets of adaptor) Now, you only grind the motor pod two times & it fix the problem forever. Right ?
What if it is a deviation of the mould of plastic adaptor which will be fixed subsequently and your motor mount had already been ground. Why don't you tell World about this?
Yes, maybe someday the manufacturer will fix this problem ( to enlarge the ID of the motor pod or making the plastic adaptor in smaller OD). For existing S120 users all they can do is to do some modification themselves.
The CRC 1/12 has the same problem like this, and recently they launch a new small OD plastic adaptor to address this issue, and require no modification at all.