PS4 No DRS & poor engine performance after update.

[Colinzzr 0]

Version 1.05 on PS4
Since updating on 24/09/16 I have been having problems in career mode. 
Game starts fine until around half way through the race the DRS flashes but does not activate and I get reduced engine performance. I go from being a second a lap faster than other cars to being around 2 seconds slower (very frustrating).
When I start the next race the problem persists through practice. It sometimes clears if the PS4 is rebooted but not always.

HELP!