Auto Line straightening feature with Apple Pencil not working in Books on my iPad.

Lines and figures I hand write in a pdf inside the apple Books app used to get 'straight' when I maintained the pencil tip for a few seconds in the end point of the line. Suddenly it stopped doing it. It still does it in other apps like apple Notes and others.

I am not aware of any parameter that governs this behaviour, and that does not happen in another equal iPad with same level IOS and apps, so something happened to my pencil or iPad that I cannot figure out.

I did uninstall and install the apple Books app but the error persists.

Any ideas?

[Re-Titled By Moderator]