Power discrepancy

Seen this issue twice now over last 2 weeks. Once within meetup session and once in TTT event. For meetup rider was pushing 3wkg power, but when i looked at rider session, it was appearing as 2wkg. This evening i seen issue again for a different rider who is high CAT B and experienced zwifter. He was pushing 4+wkg and this was displayed on his screen, but our team noticed his output as 2.1wkg. 2 separate incidents. First rider on kickr direct drive and 2nd rider on new wattbike atom. Any thoughts?