Wow I wish my printer would be that level. Out of all 5 I have had now, all of them but one where worse than 0.5mm difference, and the one that wasn’t was the one with the bad laser flare. 
On this last one they told me they make sure that all of the printers are parallel, and they made a special effort to make mine parallel in particular and after a couple tries they gave up and said they couldn’t do any better than 0.55mm and just sent it back. I’m so sick of this whole thing.
That sucks @RocusHalbasch! Where is the origin of the difference? Can a new build platform improve or decrease the difference?
i ended up with minimal difference when setting the build platform at 0…5mm higher.
I haven’t checked that. I actually haven’t even opened it up yet as I was trying to get them to tAke it back and make it right but they refused. All I know is that when the squares are printed their thicknesses vary by half a millimeter. This in my experience usually means the tray housing itself is not perpendicular to the z-axis which causes the entire print to be skewed. I plan on doing a full write up of how all of that works and how to test for it, including illustrations.
Rocus, I purchased my 1+ second-hand and had an unsuccessful print which didn’t stick to the build platform. I was concerned about the base/tray height until I tried your platform test. Take a look at how poorly mine did:
Needless to say, I’m concerned… and don’t even know where to start!
Amit_oberoi,
Have you tried the X-Y tuning? 
@Amit_Oberoi
Looks like your galvos are twisted in their sockets or the potentiometers on the galvo controller board are not right somehow. This is usually a matter for Formlabs support if it is still under warranty, as attempting to fix this yourself would void your warranty. So if you haven’t opened a ticket so so right away.
@Cheuk_Ming_Wong
X-Y tuning will not help. Those settings only do scale.
yikes. thanks man, im going to find out