Hi Darabillions,
To begin, we want to make sure your iPhone 14 Pro is updated to the latest version of iOS, as these updates often include fixes for unexpected behavior. Update iOS on iPhone covers backing up your device and updating if needed.
"Update iPhone manually
At any time, you can check for and install software updates.
Go to Settings
> General > Software Update.
The screen shows the currently installed version of iOS and whether an update is available.
To turn off automatic updates, go to Settings > General > Software Update > Automatic Updates"
After updating, try using Siri to add a calendar event to your device again using the steps in Create and edit events in Calendar on iPhone.
If the behavior persists, contact Apple Support.
Take care.