The game failed to save. error code + completely deletes save

I keep trying to save my game & upon first launching up my game it saves perfectly fine but about 10-15 minutes in whenever I try saving I get an error code saying:

The game failed to save. error code: 21 

however it’s not occasionally like this, this is every single time I play the game

 & also it’s not consistent with the error code it says 21 now but it changes every time I try save the game and I’m on Xbox so it’s not a problem I could even cause if I tried but regardless it’s definitely not great

if there’s a fix for the game failed to safe error then PLEASE let me know I genuinely just want my game to save I don’t want to lose hours worth of gameplay especially considering the fact that it deletes the entire save (like if I go to save game - then click on whichever save I wish to override - it has the saving game loading thing - then it will show the error code - then I go back to look through my saved games & I see that its completely deleted from there + the autosave is completely gone as well - which completely deletes its not automatically restored upon relaunching the game) 

& another glitch (completely unrelated to this one I just figured it’s worth mentioning to ‘kill two birds with one stone’ I guess) that I’ve also seen other people having that I’ve been experiencing a couple months before this error code saving glitch started happening is that after a couple hours my game crashes completely sometimes but that ones at-least bearable for the meanwhile until a fix the save game problem however is not 

(am not sure what tags are applicable here so Im just using what I’m hoping is correct)