Ok I think I might have got to the bottom of this.
I've been digging in the shed. Here's three springs -

Top one is Li, no kink, smaller.
Middle is an old worn GP one been rubbing on the clutch. Larger with kink.
Bottom is the new one, GP with kink.
This pic shows the worn spring top, next to the new one.

Here's the Li one in an Li casing, right and the GP one, left.

There's no difference in the positioning of the recess in the casing.

Looking at the both the Li casings I found it definitely seems that it's common for the spring to rub on these ribs.


Anyway to cut to the chase I tried the old worn shaft in the casing and it seems fine. I checked the dimensions on the shafts and these are the same. The one difference seems to be the depth of the hole in the shaft for the spring. On the SIL one it's not deep enough. This appears to be enough to force the kinked part of the spring into the ribs.


Thanks for everyone's input, tomorrow I'll drill it deeper and update.