Sometime happens, not always.
I’m using up to date iOS and DTTG with 2nd gen pencil.
Which line(s) is(are) do you consider “strange”? The ones you drew freehand (maroon) or the red “arrows”. Arrows are a drawable objects on an iPad, as are the free-hand lines. I don’t tend to draw into DEVONthink ToGo, though.
If you look a bit closer, you might notice two thin vertical lines departing from the thick horizontal lines – approximately at the points of the arrows. I guess that the OP drew the latter to draw the attention to the stray lines in the drawing 
Yes that’s right.
my eyes getting old… didn’t see them on my monitor (colours blended). I can only guess what the cause is, but hunch is it’s something to do with Apple’s Pencil software. First step should be I think to restart the iPad and see if they go away or if can be replicated.
Also to help ascertain what the lines are and if they are part of the file or something else, i.e. the Ipad just decided to do it for some reason:
- convert the document into another formats, e.g. PDF and see if these lines are there
- possible to erase them in this document with the penci’s erasure mode?
- save and reopen the file
- if you sync with a Mac, does it show up there also?
if i choose eraser, this vertical line will disappear, but when choose painter the line will appear again.
I think it’s not a real line in PDF.
Does this sort of thing show up when using Pencil in other drawing/note apps?
I find maybe the tip of my apple pencil loose a little bit, i will keep you posted if happen again.
Thank you!