If the Solflare app keeps crashing, first update it to the latest version and restart your device. This is because older builds often break after changes to the Solana network or operating system.
Also, make sure your device has enough free storage and RAM, since low memory often causes freezes.
To get rid of bad data that can make you lose connection over and over, either clear the app files on Android or reinstall the app on iOS.
Make sure your internet link is stable, and don't use a VPN, which is known to mess up Solana RPC connections.
If you use Ledger and Solflare together, make sure that the Ledger software and the Solana app are fully updated, or else they might crash when signing because the versions don't match.
If the default node is unstable, try changing RPC destinations in the Solflare settings.
If the issue doesn't go away, you can contact Xolvie to find solution.