Imagine you are grinding in on a jib sheet. Just as the jib comes perfectly taught, you look down and realize you have a deep override on the winch. You yank the tail to free it, but the tail has buried itself under three tight wraps on the winch and— nothing. You try pulling on the standing side of the line going to the clew of the jib, but the sail is pretty snug and full of wind — nothing doing here, either. Eventually, you will need to clear this jam to tack, change the jib’s trim, or douse the sail. You could cut the line, but then you’ll have destroyed a perfectly good sheet, and you’ll lose control of the jib.
You used a machine to get into this situation; let’s use one to get you out. Do you have a winch you aren’t using? Excellent. Grab a spare line and tie a rolling hitch around the standing part of the jammed sheet. Lead the tail of this line around a spare winch. If the spare winch is not in line with the jammed line and the jammed winch, you will need to use a fairlead, like a block or even a cleat base, to align the pull direction with the jammed line, and pulling in the direction of the jammed winch.
Wrap up the spare winch and take in slightly. All you should need is an inch or two of slack going into the jammed winch. Work that slack in and around the jammed winch until the override loosens. Re-wrap the winch properly, cleat it off, release the line from the spare winch, untie the rolling hitch, and keep on sailing!