I have a feeling that the spec of the spring was changed in early 80s and that this wasn’t (such)an issue with later bikes.
There was certainly a spate of such failures in the 1980's, & it was annoying as it left you stuck in whatever gear you had been in, if you see what I mean? With much burning of clutch I managed to ride home, a good 50 miles, in third, which was probably the best gear to be stuck in. The local dealer produced a new spring & said "We've sold a few of these lately....." The replacement is still going strong, some 80,000 miles later.