I've always greased the fittings at the pedals and I applied a generous amount of PB Blaster to that area. The return spring looked ok, probably couldn't overcome the binding. It's been soaking a few days, I'm crossing my fingers.
Mine seizes up where the shaft enteres the brake housing. Have to crawl under with the penetrating oil and hammer. Tap the linkage into the release position, squirting oil. have the helper apply brakes and do it all again until they move freely.
Definitely a two person job. Best way to prevent it is to USE THE BRAKES, even though you seldom need to with HST....
i'm pretty sure this is the parts breakdown for the shaft in question here,
let me know if not, but you want to lube/work that shaft going
into the side of the housing so it doesn't bind and releases fully.
really just working it with some lube is all it should need, a helper makes the job
go quicker for sure.