Official comment
Hello Conor,
Sorry for the inconvenience with the FX2 knob.
Engineering team has successfully replicated this issue and now working on the fix.
A new beta version will be released in the Forum page when the fix is ready.
If you would like to downgrade to 4.2.5, please download and install it from the link below.
https://www.dropbox.com/sh/ydx3m963x88nyfg/AABCLBTn9kkREBMN3Yo2yVwpa?dl=0
Thank you very much for your patience until the fix is ready.
Best regards,
CRM, Pioneer DJ