Y Axis squeak, possibly ACME nut blocks?

I’m just getting my 750x750 screw machine commissioned and I’ve run into a problem with the y axis.

When I first tested the y axis movement the whole gantry went out of square and there were a lot of mechanical ‘complaints’ from things binding and griding.

I did a quick read and discovered that I hadn’t tensioned things with the little hand wheel.

This was done and the gantry now moves straight without the binding and grinding, but I’ve got some nasty sqeaking noises that come and go as the lead screws turn.

The noise seems to be from the Y plates - I’m guessing something to do with the ACME nut blocks. The wheels seemed fine during the initial mechanical build.

I’m presuming that this is a common set up issue and I’d like to avoid disassembling too much in a random attempt to fix it!

Any help appreciated!