Guides, margins, and bleeds cannot be set and have display errors on the iPad.
They cannot be set when you are using art boards (they jump back to 0), and when you have multiple art boards, the margin shows up in the wrong place.
I noticed margin display error it when opening a document I’d created on my Mac - they are right on the Mac, but display wrong on the iPad.
I’m using 11” iPad Pro, affinity designer 1.8.4
linking the original thread from the pre-p 1.8 beta archive as these have been issues since 1.7:
plus here’s a video of the margin display error
RPReplay_Final1598999987.mp4