Hi Colin, the bug had to do with the keyboard focus code trying to target an input control on the construction line popup menu (the one where you activate the "Relocate cline" from) even though the menu is actually hidden at that point.

I've got it fixed up now for the next beta, thanks for reporting it.

Also one other quick note - if you enter in a single number other than 0 inside of the XYZ input (the one where focus first goes when you push Tab when it's working ok) that will also be taken as a distance constraint. And also if the command itself does not have its own input fields, if you just start typing a number that keystroke and the focus will go into that XYZ field without needing to actually hit tab. So usually (aside from this cline bug) you can just type in your distance constraint number without needing to hit tab at all, just type in like 5 and push enter when drawing a line to activate distance constraint of 5.

- Michael