I want to make sure I'm understanding you here.
So you're saying that the 1000s reel is turning over OK up until you have 9000 scored on the game? And then when it attempts to go from 9000 to 10000, the 1000s reel is hanging up?
If the reel is turning fine until you get to 9000 and attempting to go back to 0, you have a switch adjustment issue. Decagons are notorious for hanging up at this point. It's caused by the 9 position switch putting too much pressure on the follower which causes drag on the wheel. If it's working perfectly on other numbers, it's not a power issue.
I think El Dorado was made after they switched to the final version of the decagon-it no longer has the wireform that moves the switches. Still, I'd suspect the 9 position switch. It needs to be adjusted so that it just makes when the reel gets to 9.