It’s definitely due to the electrics at the venue as the night before the other entertainer also had a problem with equipment.
And I performed with it last night and there was not tuning issue at all.
The out of tune was not on the backing track...
Just a warning if you have the Roland Bk9, I was performing a song and went to do a piano solo and it was completely out of tune.
When I got home it was absolutely fine, which indicates the problem was possibly the electrics at the venue..
I had this same problem it cost me around £80 I can recommend an engineer if you require assistance.
It's a part the controls the sound on the keyboard.
Did you notice a crackling sound when you turn the volume or anything up? because that is a sign...