How do I fix a horse that has lost its stop in cattle work?

A horse that stops correctly in reining work but loses its stop quality in cattle work — not stopping as deeply, bracing through the stop, or running past the stop cue when cattle excitement is elevated — has developed a pattern in which the cattle context overrides the trained stop response, and fixing it requires addressing both the underlying cause and the specific training response that restores the stop under cattle conditions. The most common cause is that the cattle work has been conducted at speeds and excitement levels that exceed the horse's ability to maintain its trained responses, essentially drilling the cattle work at a level of intensity where the horse was consistently getting away with reduced stop quality, which gradually erodes the standard in that specific context. The training fix begins by reducing the intensity of the cattle work — slowing the pace, using easier cattle, working in a more controlled environment — to a level where the horse can and does stop correctly in the cattle context, and then building intensity back up progressively while maintaining the stop standard at each level. Alternating between reining stops without cattle and stops requested in the cattle context helps the horse maintain the connection between the stop cue and the response regardless of the presence of livestock. The stop must never be allowed to go uncorrected in the cattle context even if the correction means disrupting the cattle work session to address the stop quality separately before returning to cattle — consistently allowing the cattle environment to produce a below-standard stop teaches the horse that cattle conditions are an exception to the stop requirement rather than a context in which the stop must be equally correct.