Gantry off set

I’ve tried everything from tightening and loosening screws to putting material in between the gantry to try and fix the slant that it has but nothing really seems to work. Does any of you have any suggestions or answers for me?

I’ve tried everything from tightening and loosening screws to putting material in between the gantry to try and fix the slant that it has but nothing really seems to work. Does any of you have any suggestions or answers for me?