Dont know if its fixable, but if you sell a lot of different things to a vendor (300+ items) and then visit him again and trade with him it tooks very long to load his inventory sometimes the game crashes. It must be a memoryissue.
I tried it out on 2 different PC's. The components of the PC take influence of the loading time, but if u sell enough to the vendor you can get every Machine to its limit.
Latest Version of Definitve Edition
No Mods used