TAZ6 bed gap to nozzle far greater one one side after auto-leveling is complete

After the auto-level has completed and I start a wide print that almost fills the x axis, I can visually see the nozzle gap is far greater on the left than the right. As much as a 1-2 mm. Is there a way to check the capability of the auto-level function?

When the auto level routine is tapping the corner washers, are the washers being pressed downwards at all? If so, warm up the nozzle and scrub it with a piece of green or blue scotchbrite.

If the corners are being tapped without any deflection, try this:

Jog your toolhead so the nozzle tip is ever so slightly above the front left corner washer.
Turn the printer off.
Slowly move the toolhead to position the nozzle over the front right corner washer.
Manually turn the right leadscrew until the nozzle is slightly above the washer. Visually match what the left one looked like.
Move the toolhead back to the left washer and adjust with the leadscrew.
Continue alternating until the nozzle is above left and right washers by the same distance.
Use the nozzle to do this rather than a dial indicator. The nozzle is the thing that matters.
Run a test print.

Also worth checking that your washers are flat to the bed – they should NOT be tilted up on any side, and they shouldn’t move if you try to rotate them by hand.

(Basically, the auto-level mechanism levels with respect to the point where the nozzle makes electrical contact with the washer, and the bed is determined to be your “z-offset” value below that level. So, if your washer is tipped, then the z-offset to the bed for that corner will be wrong – also, if your nozzle touches the side of the washer, then your z-offset for that corner will also be wrong – and as nopick suggests (above), if you have plastic debris on your nozzle that requires the nozzle to push down on the bed before it can make contact, then too you’ll end up with the z-offset on that corner being wrong… lotsa things can possibly go wrong, but some basic maintenance checks and cleaning will prevent the vast majority of them.)