Nothing happens at 86%, because that number doesn't mean anything, since is related to the number of sceneries you have. It might simply represent a certain amount of time, after which the sim crashes.
If you had less sceneries, it's likely the crash might have happened AFTER GSX completed the regeneration of its cache. But if the sim crashes before GSX can complete the cache regeneration, it will start again on the next session so, unless you find a way to fix the crash itself, it will never be completed.