Answered Uneven bed on Robo 3D R1

Unfortunately the auto-leveling used in the R1 firmware can only detect unevenness in one plane (X or Y, not both) so you end up with situations exactly like you explained. This is not limited to the Robo R1/R1+ but others printers using the same Marlin firmware also exhibit this behavior.

How to fix it is by carefully leveling the bed from front to back so that it is as even as mechanically possible. I did this with a piece of self-adhesive shelf paper (Contact Paper) and a hole punch. I punched a lot of holes in a small piece of contact paper and kept the little discs that are usually thrown out. Popping the bed of the magnets I used those little discs one at a time with the backing paper off (so they self adhere) placed on top of the magnet under the low corner. I kept doing this one disc at a time until I was level from front to back. This way every corner of the bed was even with the highest corner. At this point your bed is as mechanically level as possible.

Now the auto-leveling has less to do and can better compensate for a bed that is tilted. It may seem like a lot of work, but it will pay you back in rewards of less fuss with leveling the bed.

 

A bit of shim steel works fine too

https://www.amazon.com/Precision-Carbon-Assortment-Temper-Chemistry/dp/B00065UX42