To resolve the issue of your app closing unexpectedly during transactions, follow these comprehensive steps:

1. Force Close the App
Open your device's settings, navigate to 'Apps' or 'Application Manager', find the problematic app, and select 'Force Stop'. This will stop any active processes the app may be running.

2. Clear App Cache
In the same app settings menu, select 'Storage', then tap on 'Clear Cache'. This action removes temporary files that may be causing the app to crash.

3. Restart Your Device
After clearing the cache, restart your phone. This helps refresh the system resources and may resolve temporary bugs or conflicts.

4. Update the App
Ensure that your app is up to date. Go to the Google Play Store, search for the app, and check if an update is available. Installing the latest version can fix any known bugs that may cause crashes.

5. Check for System Updates
Sometimes, app issues arise from outdated operating systems. Go to your device's settings, look for 'Software Updates', and install any available updates for Android.

6. Reinstall the App
If the problem persists, uninstall the app completely and then reinstall it from the Google Play Store. This action can address deeper software issues that a simple cache clear may not resolve.

7. Monitor Device Storage
Insufficient storage can lead to app performance issues. Make sure you have adequate space available on your device. Go to settings > Storage to check your available space and delete unnecessary files or apps if needed.

8. Check for Compatibility Issues
Ensure that your app is compatible with your Android version and device model. Sometimes, issues can arise from the app not being optimized for certain hardware configurations - learn more - learn more.

9. Contact Support
If none of the above solutions work, consider reaching out to the app's customer support for further assistance. Provide them with details of the issue and the steps you have already taken to troubleshoot.

Implement these steps systematically to address the app crashing issue effectively. If the problem continues, there may be underlying issues specific to the app that require developer intervention.