First 1903a3

[Doco overboard]

Could just be that the bore that little plunger works in is sticky from dried oil or whatever causing it to drag when the switch is being moved. The bottom of the bore could also have build up in it.
If there is dried cosmo/ grease hardened in between the coils of the spring it may reduce its ability to compress or float over the reciever surface.
That little plunger usually has a very small teat that could also be flattened/slightly worn which makes for greater resistance. Coils bound, etc.
The spring that goes over the plunger is unique and small /strong so it very well may have been lost-replaced if someone had it apart.