It could be that, or some stickiness in the pedal or linkage somewhere.
On that shaft, you need to use a smear of dry 'assembly lube' type product, that will not run off or be a dirt magnet.
The best of these are Molybdenum Disulphide based, and contain a very high percentage of it [~50% for the pastes]. There are spray can and paste forms available, from industrial [e.g. bearing service] suppliers. Rocol, Molykote and Dow Corning Molybond are three good brands of these.
But be warned, they aren't cheap. If you have tradie mates who work in heavy industrial maintenance, they can often get hold of some.
A good cheaper alternative is to get a can of 'PTFE Dry Lubricant Spray' from Jaycar Electronics, if there's a branch/agent handy to you. That stuff is under $20, and works very well. Do shake the crap out of the can before spraying, though.
It has a lot of other uses too; e.g. it makes zippers really slick! Much better than CRC Dry-Glide etc.
