Hey there Bgs006,
Thanks for reaching out to the Apple Support Communities. To get started, does the issue occur when trying to edit all videos, or just specific videos?
Also, does the issue persist after restarting your iPhone? If unsure, give that a try with the steps shown here: Restart your iPhone - Apple Support
How to restart your iPhone X, 11, 12, 13, or later
1. Press and hold either volume button and the side button until the power-off slider appears.
2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo.
How to restart your iPhone 6, 7, 8, or SE (2nd or 3rd generation)
1. Press and hold the side button until the power-off slider appears.
2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button until you see the Apple logo.
While restarting may seem like a simple step, it can often help with resolving some unexpected issues like this.
If still having issues after updating, are you currently updated to the most recent iOS? If not, since updating can often bring the latest features, security updates, and bug fixes, we would recommend updating the iOS and test the issue again.
For steps on how to update the iOS check out this next link here: Update your iPhone or iPad - Apple Support
Update your iPhone or iPad wirelessly
1. Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see more than one software update option available, choose the one that you want to install.
5. Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.
Keep us updated on the results.
Regards.