M series are going OK these days, sure they should have been going OK about 5 years ago but it is what it is. You can also set up what grade hyd oil is in the machine by programming the ECM with the info, the "brains" will then alter things to provide more optimum performance, get this checked and rectified if it is not correct as per the oil you are running, and get it checked you have the right oil for the temperature you are working in too. The latest software gets rid of nuisance fault codes especially with the steering, if you continue to get codes you will have to much movement in steering joints most likely but get a steering calibration done after installing new software if that is what ends up happening and also get a wheel alignment done, go through all the basics first, after that you may have a tire issue or an internal leak on the steering cylinders.
You can check the cylinders fairly easy, circle the blade around onto the front tyre and have it touching top and bottom, then steer into the blade so you stall the steer function out and then listen for oil bypass in each cylinder, a heat gun can also be used to check if there is heat generation where the oil is being "squeezed" through.
Good luck.