Dimensions in Rhino don’t always behave in a stable consistent way. This has nothing to do with coincident points, I think it’s a bug related to associativity. But there’s no doubt that between sessions and likely during them, on any layout with more than about ten dimensions, a perfectly otherwise good dimension or two - adhering to John’s standards of good drafting practice - on any sheet will disappear from position and show up many page widths away from the layout spaning hundreds more units than it originally did. (the corrupted dimension may in fact have coincident points, but that’s not the initiating problem). The Sproinging Dimension Problem It’s been like this for years.
This is a big challenge. It’s more likely to happen with more dimensions, so it tends to crop up when a drawing is closer to being issued. Then one must scour the drawing looking for a dimension that might be missing during the final crunch to get a drawing out. It’s stressful.