brake light switch needs spring on pedal?
 

I have had my master cylinder replaced on my '91 1st gen 12 months ago.
Now the pedal seems to 'fall' and leave brake lights on.
When at the servicing shop for the fix it under warranty for the work, I am told that the master cylinder is fine, the switch is faulty, put a spring (bunji) on the pedal.
The pedal has more movement than when first done but only 3/4 inch.

does anybody know what is it telling me--bad shop or bad master cylinder?

thanks, onlystock