Hello Patddfan,
Thanks for using Apple Support Communities! We understand you are seeing some issues in Safari when filling out web forms. We are happy to help provide some guidance.
To start, we want to make sure that the iOS version on your device is up to date. iOS 14.3 is the current version of the software. If that isn't already installed, please create a backup of your information and then go to Settings > General > Software Update to start that process:
Update your iPhone, iPad, or iPod touch
If the issue continues after you update your software version, or if you are already updated and the issue is persisting, please use the following link to contact Apple Support directly to investigate further: Get Support
Best Regards.