Sounds like your phone is running out of memory so the OS kills Boost. It's still Boost's responsibility to save its state when it is shut down by Android and restore it when you go back, so I guess it doesn't do that properly. But the problem won't be as noticeable on a high spec phone.
Boost For Lemmy
Community of the Android app Boost for Lemmy
Had this issue on a low spec phone, and it was happening for many apps, not just Boost. Could that be it, maybe?
Some brands are more aggressive with killing inactive apps than others. It would help to know which phone OP is using.
Well android duuuuh
Jk it's MIUI from Redmi 11 Note something
And yes, they are aggressive in the killing app process. Each apps, when installed, has the "power saving" setting set to "kill when inactive" which is REALLY annoying
Have you tried changing the power saving settings for Boost?
Boost should save its state to disk and restore in case the app is killed, but it is pretty complicated with an app this complex. Top apps i.e. Instagram don't do it either.
This may not be the right community for this, but have you tried Jerboa? It's a very lightweight app, it doesn't have the same features as Boost but maybe the lighter app will be a better experience on your phone?
Are you nearly out of storage space? If you run out of cache space it can run into this type of behaviour as well.