The tubes wear out on all artillery pieces. These have all been being used for months now.
Also tracked vehicles are very maintenance intensive. Wheeled vehicles are much easier to keep in service.
Somehow, Russia artillery pieces do not wear out under sporatic use....
There are other mechanical components also that break or wear out. I recall a mention early on after the M-777 howitzers arrived that the US was surprised that they shot up a few months of ammo in one month.
The description of shooting special ammunition at too great a distance is a dumb statement. They are using standard types NATO munitions that the weapons are rated for.