I know there’s a problem with the save file in ACNL. Although there is a fix for it somewhere in the subreddit, it’s complicated and time-consuming, and you have to do every time.
The best way is to get ACNL: Welcome amiibo. It’s an updated version of ACNL that has new features like the camp, coupon system, and amiibo functionality. It works perfectly without any crashing. You may want to use this version since there’s no game update support on Citra (even though you can install CIAs), so this game already comes pre-updated.
Just don’t open the “instruction manual” furniture. It’ll actually proceed to load the manual from the 3DS system, which is also not supported yet, causing the game to freeze, but you won’t face Resetti (Because you haven’t made the center yet at this point).
You can’t transfer your ACNL save file to ACNL: Welcome amiibo since it needs to insert the old ACNL game card. I don’t know if you can do this manually or not.
Hope this helps you a lot!
EDIT : Use the ACNL game that has Welcome amiibo update included in it. Patching the original one with the update doesn’t work at all.