828 is height encoder (ECR4) and/or height switch reset fail. Basically the reset switch didnt trip or it tripped at a point when the counts on the height encoder were off from where it should be. I have found this happens a lot when an operator travels a long an isle picking going up and down but not going all the way down to "reset." After the extended time, ECR4 end up with the counts off and creates the fault. Most commonly lowering all the way to ground then lifting platform above reset (about 4' to 6' off the ground) then back down resets the counts/fault and full speed travel will be resored. If this does not work or if the fault continues to come up you will want to test your reset switch and or your height encoder. If you have the cable style ECR4... Have fun! These cables are common for breaking but are pretty easy to replace. Just be careful!!! The preloaded coil spring inside there cand tear you up like a mountain lion! about 50X what a 30' tape measure does. I had one get away from me one time years ago... Not fun!