Trying to troubleshoot a Bostomatic BMC 12 with a Heidenhain TNC 426 controller, built circa 2001. A few days ago I powered it up after a long hiatus and was greeted with a "exchange buffer battery" alarm. Popped open the Logic unit and swapped the battery out. Powered the machine back up and the alarm was gone, everything seemed like normal afterward. Not until I pressed the manual data input button did I realize something was not quite as it should be. Immediately upon pressing the button, the MDI dialog was shown on the display, but the machine attempted some kind of strange tool change procedure. The Z-axis was retracted, the X-axis was centered, and the tool tray extended as it normally does, but then the spindle draw bar was extended, dropping the currently held tool onto the bed, and finished with a 40 timeout draw bar down error. The machine parameter files seem to be intact, I can jog the axes around and trigger the soft limit alarms for them. From what I understand, the machine parameters are not retained by buffer battery current, but are stored on hard disk, at least that is what I believed, but now I'm starting to doubt myself. Not sure if this is a controller problem, or a response to some proximity sensor malfunction. The draw bar timeout issue may be a cracked hose inside the Z axis enclosure, as I can hear air leaking from inside, but it still doesn't explain why the machine up and decides to do a random tool change if I simply switch screens to MDI. (It also happens if I change to the program run screen) Anyone out there run into this type of thing before?