I've had the same problem on a HP Elite X2.
I noticed it straight after upgrading to 1903. I rolled back to 1809 and the problem went away.
I've since been automatically upgraded to 1903 and the problem is back.
A couple of things I've noticed - when I first logged in after 1903 installed, this problem did not happend.
When I subsequently restarted my PC and logged in again, this problem came back - There was no update installed during this restart so it seems there was some internal config change between my first login and the restart.
As a work around, I've noticed that some of the textured pen settings (Galaxy, Rainbow, Ocean, Silver) don't suffer from this problem. For me it only affects solid colour pen / pencil settings.
Right now, for me, the Ocean pen on a thin stroke setting is an acceptable workaround for regular ink entry. a proper fix would be nice though.
I've logged this on the MS feedback up also. https://aka.ms/AA66hct
If everyone affected on this thread could upvote it there, MS might take notice.
Rgds,
Paul