1999 Subaru Legacy Sedan trip odometer problem

A few days ago, I noticed that the tens-place digit of my mechanical trip odometer no longer comes into full view by itself, that is, aligned with all of the other numbers, but the wheel continues to spin when appropriate. Instead, half of the correct digit and half of the previous digit are always showing. For example, after I had gone 132 miles, it displayed "1 [half of 2, half of 3] 2, " and after 147 miles it displayed "1 [half of 3, half of 4] 7, " and so on. How can I fix this? Where can I find any necessary parts? My dealer told me that the whole odometer needs to be replaced. Also, I should mention that shortly before this problem appeared, I reset my trip odometer while the car was in motion.