I am trying to build a 5' by 12' frame for a gate. I had no trouble at all using structural coupling to to connect two pipes to make the 12 foot segments.

I am struggling with the 90 degree connectors. No matter what I do, they seem to tighten down at an angle and don't grip well. I am using the 3/4" inch connector and 3/4" EMT.

Two possible problems that I've thought of:
1) I am building a rectangular frame, not a cube, so there is no pipe through the central hole.
2) When I opened up the connectors I thought the plastic shrinkwrap-like material was packaging and cut it off.

Any suggestions for how I should resolve this?