Hello TristanLM,
Thank you for reaching out to Apple Support Communities.
Which app are you sharing while using screen share? This may help:
"Share your screen
- Start a FaceTime call.
- Tap the Share Content button
. - Tap Share My Screen
.
Everyone can see what's on your screen until you stop sharing, but they can't control anything on your device. If you get any notifications while sharing your screen, others won't be able to see them.
When you're sharing your screen, others won't be able to see content that requires a subscription, a free trial, or a purchase or rental to view. With SharePlay, you can watch video together, listen to music together, or work out together by sharing content through supported apps."
Additional details can be found here: Share your screen in FaceTime on your iPhone or iPad
Can you provide a few more details? What is your exact iPhone and iOS version? Does this happen with multiple apps? Are you ale to screen share with other contacts? Also, have you tested with any other devices?
Cheers!