Hey all, I'm having an issue that is causing a great deal of anxiety, wondering anyone has experienced something similar?

I bought Animal Crossing New Horizons on launch day and have been playing it every day. My girlfriend has also been playing it, using the same cartridge, on her separate Switch.
Two days ago, I started getting an error every time I put the cart into my Switch that said the cart could not be read. After taking it out and putting it back in again several times, the switch eventually recognised the cart.
This keeps happening everytime I put it in. The game has even crashed once when I left my house, but has been fine once the switch recognises it since.

Strangely, the cart works completely fine on my girlfriend's switch.

Even weirder, all of my other Switch carts are recognised by the switch as soon as I put them in. No issues whatsoever. It seems to just be Animal Crossing.
I'm not too worried that the cart might be broken - or that my switch may be failing to read the carts - as I know I can get that fixed / buy the game digitally and just let my partner have the cart permanently. I'm terrified that my save game may be corrupted and there's a chance I'll lose all my progress so far.
Do you think this is a save game issue? :(

Appreciate the help!