The clutch brake pedal should cause a tension arm to pivot when you let your foot off the pedal.
It is pulled back by a spring
Mostly what happens is the pivot point gets corrosion or the hole floggs out oval
So start by cleaning & lubing the pivot
We did not get that mower down here so I have never worked on one but this is a common problem with a lot of mowers
The other thing that causes these symptoms is a build up of cutting debris that prevents the pedal returning fully .