It’s also worth pointing out that Infinite Flight is a resource heavy application… It’s not designed to run in the background, nor is it designed to run in multitasking.
If the app is crashing during multitasking… Don’t multitask? Sorry if that seems unhelpful, but you’ve solved the issue in your own question. It’s not an issue with the app, it’s down to your device. I don’t think it’s something the developers are able to fix. 2GB of ram on your device is not a lot, and IF uses a lot of that ram during a flight. Limiting the amount of available ram can cause crashes. It’s the same on android, it’s the same on a desktop PC.