also try reinstalling CBBE, and get the ESP version of it, not the ESL file. Try reinstalling XPMSE (XP32 Maximum Skeleton Special Edition), and allow it to overwrite everything. If it is indeed complete character absence (the character is completely invisible) then the only things that i can think that could possibly cause this are as follows: invalid skeleton (XPMSE not installed properly, or you installed another mod that overwritten the Skeleton.hkx file supplied with XPMSE), missing body mesh files and or textures. Best mods to create smoking hot female characters and NPCs'.
What are your latest actions before your character completey disappears (such as do you change armor, equip a weapon, etc etc), need to get a good idea on how this happens. For The Elder Scrolls V: Skyrim Special Edition on the Xbox One, a GameFAQs message board topic titled 'XSX player here. However if it is the latter, sounds like its connected to the body, such as missing body mesh files, however that would be a constant issue rather then a random issue.
If its the former then its most likely a piece of armor that causes the invisibility when sneaking or any other condition such as in combat, Disappear as in stealth invisibility (such as sneaking with Ebony mail) or disappear as in complete absence ?