Hi there! I understand you're experiencing crashes with the VASA Fitness app when you try to check in. Let's work together to get this fixed.

First, can you tell me if the app crashes immediately when you open it to check in, or does it crash after you try to scan your barcode or take some other action? Also, have you already tried restarting your phone or updating the app?

In the meantime, here are some steps we can try:

1. Close the app completely: Swipe up from the bottom of your iPhone screen and pause in the middle, then swipe the VASA Fitness app off the screen to close it.

2. Check for app updates: Open the App Store, tap your profile icon at the top right, and scroll down to see if VASA Fitness needs an update. If yes, please update it.

3. Restart your iPhone: Press and hold the side button and either volume button until you see the slider, slide to power off, and then turn it back on.

4. Clear app cache/data: iOS apps don't usually have a cache clearing option, but uninstalling and reinstalling the app can help clear any corrupted data. To do this, tap and hold the app icon until it wiggles, then tap the 'x' or 'Remove App.' After that, go to the App Store and reinstall it.

5. Ensure your iPhone iOS version is up to date: Since you have iOS 18.5, confirm in Settings > General > Software Update that you have the latest iOS version installed.

6. Check network connection: Try using both Wi-Fi and cellular data to see if the problem persists, as a weak connection can cause app crashes.

If these steps don't clear the issue, it might be related to app compatibility or a bug. The VASA Fitness app team may need to investigate further.

Would you like me to guide you through these steps? Also, please let me know what you've already tried so I can tailor my help better.