Check voltage, which I presume is OK since you are still driving. Then swap window controllers across from one side to the other, and try again. Had same with Tuscan.
Passenger side on the Sag is a bit like that. Not excruciatingly slow, but noticeable enough. Had consistent problem with the Tuscan, came down to water ingress onto contacts on the controller.
When my Sag was in for service, the drivers window wouldnt go all the way up the day before, and they found a loose nut blocking it, all done, serviced, and some extras checked and changed, now in storage
