What could cause these leveling results on a Tronxy XY2 printer?

I got tired of the paper method and adjusting the screws by the auto-leveling results as I could never get them to be consistent. Now I used mechanical level indicator and got these consistent values indicating that the bed is tilted to the right/left?

To my suprise it can actually print something like this but what would cause these values? My suspicion is that the Z axis is sagging but I would like to get some opinions before completely reassembling the printer.