iBooks removes my highlights and moves them a few lines upwards

I'm suddenly having this issue on my iPad that as soon as I mark a sentence to highlight, the highlight disappears from the sentence and moves upwards a few lines. This happens everywhere, even when the new location doesn't have text. It moves the highlight block, so to say.

I haven't touched any iBooks or iCloud settings and no updates have been performed. To try and solve the issue, I updated my iPad to the latest OS, reinstalled the app, and reactived iCloud settings. None of this has helped so far. Has anyone else experienced this - Is this a common bug? Any ideas on how to fix this?