There is no definitive root cause for CPD hours being recorded excessively.
One common reason is users leaving modules open or not exiting module when leaving device for an extended period, resulting in the time taken to complete showing much higher than it should be in the user's CPD log.
Should this occur, there are two available fixes to correct user's CPD hours.
Manually amending a user's CPD time. Overwrite the time the user spent completing the module with the correct figure.
Apply CPD cap to users on a module. Limit the maximum CPD time awarded for a module.