That’s generally not a good thing. I think the solder and what not has already settled in so it probably isn’t that. Could be worth opening up to see if you see anything burnt inside. If everything is working as expected though, I wouldn’t be concerned if you don’t see anything visibly wrong.
Have it checked, obviously, and if someone local can’t do it PS Audio’s service consistently gets very high marks. You have a great piece of gear - it’s worth repairing.