As far as I have observed, it only happens with the page title.
I’ve found this issue quite difficult to reproduce; there is no way other than just typing until it happens. In the video I’m writing a sentence to make the issue easier to see, but is’s easier just mash the keyboard (careful not to press the arrow keys).
When I type a letter, the cursor would be to its right so that I can continue typing.
OS: Windows 10 Enterprise, version 20H2, build 19042.685
Device: Fujitsu Lifebook AH552/SL
Version: Anytype 0.17.0
My computer is very slow, which might be related to the issue.
I haven’t encountered this issue in Anytype, specifically. But I’m familiar with similar problems in some web tools like Roam when my CPU is taxed. So indeed it might be related to your slow computer. But of course it shouldn’t happen regardless.
It also happens, when you insert a new block with the “+” and then dont choose something from the list, but instead type for example “###” and then your text. When the list of formats is closing the cursor jumps to the beginning.