assembly: cannot lock idler arm/swivel
I think I'm having a problem similar to what @Printeyy described in [1] but I haven't gotten so far in the assembly as trying to run any filament through the printer. I'm at the final(?) stages where I've powered up the printer and have started doing the XY calibrations, etc. I don't really understand @Printeyy's solution. I'm struggling to figure out how it is possible to move the arm/swivel in (to the right) enough to bring the locking piece down from the top to go over it. It doesn't seem physically possible.
There's a larger version of this image at [2]
The lever (horizontal arrow) is in swung into the right most position as far as it will go, and the lock (vertical arrow) isn't even close to fitting how it's supposed to. I've removed the PG set to get a clear view of the tolerance (the very thin washer on the motor shaft behind the PG set is not shown here). Re-installing the PG set, as seems to be suggested in the other thread, has done nothing to make the situation any better.
Any help would be appreciated. Sorry the photo is blurry.
[2] 
RE: assembly: cannot lock idler arm/swivel
You have an error in the assembly. Unscrew both screws with springs, turn the entire Idler-swivel assembly by 180° and screw both screws with springs back. The screw heads, not the nuts, must be visible on the Idler-swivel assembly.
RE: assembly: cannot lock idler arm/swivel
And one more thing: before testing the locking, the complete gearbox must be inserted and screwed in.