Thank you Benny,
Here's a few more things you can try to help us pinpoint the issue, in no particular order:
- Try an earlier build as you said.
- Send us a screen recording of the issue while it happens.
- Upgrade to iOS 12 and see if that helps. Unless you have a specific reason to not upgrade, we highly recommend doing so. It seems like a solid iOS release, including the accessibility features, and can even improve the performance of your device. We recommend all our users upgrade to iOS 12.