Hey there! I’m not from the Prusa Support team but may be able to help.
Although I never got an error like you’ve described from my kit, there are a couple pointers in the MK3 manual.
Do you know/have a picture of the error message itself? Some things to check may include if the nozzle is clean, if the PINDA is clean (there may be bits of plastic on it or something), if the 3 U-shaped bolts under the heatbed are secured (or at least make sure you can’t jiggle the heat plate around significantly), or just checking if the axes can move freely. Just because the heatbed is pretty heavy the y-axis should have a tiny bit of resistance but there shouldn’t be any problems with tons of friction (or that may be a problem).
If this doesn’t help, try checking the x-axis. Even if the tension of its belt seems fine, it’s good to make sure that there isn’t too much tension. One thing that plagued me for the first week or two of using my kit was that I had the pulley on the x-axis motor on the wrong way (upside down, so that the belt was 1. grinding on the orange printed part and 2. skewing the x-axis).
I hope this helped, and good luck!