Help with fixing BPM issues

Don’t suppose anyone knows how to fix an incorrect BPM on a song do they? I’ve tried changing it in RK but it doesn’t seem to save but I’m sure I’ve tried in the past and it has.. and whether the BPM issue seems to be linked to particular tracks not working on systems such as the RX2 and XZ but do work on CDJ’s weirdly. Unfortunately don’t own a pioneer unit currently so can’t self test overly but when I do it’s always a gamble what songs work