I bought my son a lionel lionchief polar express set for Christmas. Worked great on Christmas then this morning the chuff sound makes an erratic static/vibration sound at high speed and completely cuts out the chuff sound. It works a little better in reverse but not by much. The chuff sound goes back to normal at a low-medium speed in both directions. All other bell, whistle, and announcements seem unaffected. I noticed some dirt material on the electrical contacts of the locomotive and the tender so I cleaned them up with contact cleaner. I checked all connections to the track and all seem tight. I ran it on my other loop of track with AC power and still get the same noise. I did notice one of the trailing axles is bent and it moves the copper ground strip up and down but I don't think that would be the issue. Any help would be appreciated.
Thank you
