San Diego service center fixed shudder on my 90D 2 weeks ago.
These are the parts they replaced:
HALF SHAFT - FRONT LEFT (1027111-00-B)
HALF SHAFT - FRONT RIGHT (1027115-00-B)
JACKSHAFT ASSY, FR (1030632-00-A)
WASHER SAFETY M24x39 (1020296-00-B)
NUT HF M24x1.5 [8.8] ZnFl-W (1020297-00-A)