I had the same problem with my WBB Peter Witt trolley. I ran this trolley all the time. Both the side frames and gearbox/wheel assemblies were deteriorating as shown in SJC's pictures. I contacted WBB and they did replace the the trucks and side frames. This is the trolley that I had referenced in my earlier post about the MTH P5a Box Cab casting issue.
Eric Hofberg
TCA, LCCA