Most Common Cause (if not the below)
Not building in Bodyslide with your pre-set and other Bodyslide issues... See most common mistakes in Building toys in Bodyslide
HDT Chains
If HDT chains are glitched/misplaced/disconnected/CTD check anything related to your HDT body such as skeleton and HDT Physics Extension mods (which must be v14.28 or you CTD - relevant only for LE). Make sure they are installed and up-to-date
a crash, the first time you meet a ghost, is caused by this (missing or wrong versions of Skeleton or HDT Physics Extension)
If a toy is normally fine but becomes visually glitched (for example an anal toy gets "rag-dolled" out of place on death), you can fix it by unequip/re-equip when possible, or reloading the game
For SE using Faster HDT-SMP may fix
Animated Workout Gag
Can become invisible (animations are susceptible). Use the same solution in the point above
Graphic smearing... your VRAM is maxing out, too much HTD. Nothing can fix this other than using less HDT. Restart the game
Does not look like the pictures/is not animated - this is normal if your character is male, or a female Orc, Argonian, or Khajit. It's not compatible with these head types, thus reverts to a basic model