ARBookMarks for Radio start bookmark is always 100 seconds late


Well-Knwοn Мember
Recently I've been using ARBookMarks as an easy way to help recognise if ever BBC Radio channels start using AR.
The end book mark is according to the schedule.
Because the start bookmark has been in an an unexpected location I've recorded some of the same programmes with a couple of my other recorders (Youview DT2100 and Vestel T7655). ARBookmarks is placing the start bookmark always about 104 seconds late compared to the start of the recording with the other recorders.
ARBookmarks appears fine on the TV recordings, it's just with Radio that it is out.

Can anyone explain why this happens with Radio and not TV recordings?