The bug has unfortunately returned in Elsweyr Update 22, but the old trick of unequipping and reequiping a Prisoner's Rags item no longer works. I've tested a ton of permutations of sprint cost reduction buffs, but none seems to get the cost reduction to 100%. Still, it's pretty close to 100%, and the drain is slow enough that periodically drinking a trash stamina potion should be enough to let you perma-sprint with Darkstride+Prisoner's Rags.

My preference these days is more for sprint speed increases, though. For farming, if you need to sprint so long that you are exhausting your stamina, then you would probably be best served to get on your horse. I'm going to experiment with farming builds, but my instincts tell me that something like Cowards Gear + Darkstride or Fiords on an Orc with Swift jewelry and Dubious Camoran Throne drink and trash stamina pots will be the best balance.

I'm happy to report that this addon is no longer necessary in Update 18 Summerset. If you unequip and re-equip a Darkstride item, the bug still comes up, but it goes away again once you re-zone, which is exactly the same behavior as this addon.

During testing, I found that if you unequip a Prisoner's Rags item and then re-equip it, the problem went away until you rezone. This addon does the unequip/re-equip automatically.