WIP (6.0.17304.10081, 31-10-2017)
When selected multiple edges and try to move to a new length with gumball, something strange happens.
I ad 3 pictures.
first one shows the selected edges
second one shows after gumball movement (+/-1mm in Z direction with yellow arrow)
third one shows after zoomextends
That doesn’t look right - can you post the file perhaps (or send it to McNeel directly)?
I’m not sure this should be under the Mesh WIP category though, looks like these are not meshes you’re editing…
My guess is that you have cylinders part of booleaned objects. That generally doesn’t work well when trying to move edges of such cylinders or tubes. You’ll have to untrim them, then reapply to boolean operations.