Survival: Endless isalmost impossible to play on NS2

When playing survival: endless, there is a good chance (I’d say 75%) that when reloading into a save it will display for a second and then immediately wipe it, starting you at the first flag. This is already bad, but after flag 50+, the game almost always crashes, I’ve never gotten to 65+. Please, please fix this because it is almost impossible to play this mode when your data wipes every time you try to save it. (attached are videos of this happening)

Thank you.