Donkey Kong arcade issue: Footstep sounds monotone

[Kyou-kun]

I'm looking into buying a nice Donkey Kong machine, but the one that I'm interested in has an issue with the footsteps; all of the footsteps are monotone instead of fluctuating in pitch like they normally should. I heard a little while ago from somebody in Xermon54 (the guy currently trying to break the Donkey Kong world record in Denver)'s Twitch TV chat that it maybe be caused by a broken transistor, but he said he never experienced or looked into the problem himself. I can't find anything about this on the Internet, so I've turned to this website. Have any of you ever heard of this issue on a Donkey Kong machine or know what is likely causing the problem/how to fix it, and whether or not it's an easy, inexpensive fix?

Here's a video of the machine in question, with the footstep sounds being heard starting at 0:43:


Thanks.

[Gray_Area]

Ask at KLOV.