Pin 1 to Pin 6 is correct, 100k is correct, center wiper and one end are correct...
Schematic
Are you sure about the pin numbers? 6 and 9 look similar and are on the same side. Oh, you measured.
Try putting a 47k (fixed) resistor (or similar, anything between 10k and 82k) across those pins and see if that gives you a non-254 reading.
Strange, it's probably something simple. Have someone completely unfamiliar with it check it over, draw a simple schematic showing what you think it is, and have them check it for you. This works more often than you think.
Don