I started getting that a year or so ago. No more arrow if I pressed the button on the side of the shift knob. When the arrow is on, it means the transmission is prevented from shifting into overdrive, which is what you want for hauling a heavy trailer. In my case, last I checked, the arrow still worked when in Park, so I expect it's a wiring problem, but it doesn't bother me enough to dig in there and check it.
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1992 745, >500k km