Steam Class 20 Nuclear - Throttle Lock

I'm attempting 6A73 on London-Milton Keynes, and despite having succesfully driven the Class 20 Nuclear before, this time I'm not able to get rid of the throttle lock.

I've inserted the master key, set the reverser into forward, and fully released the brakes and waited for the brake pressure to charge. Even while attempting to use the throttle, throttle lock stays in place.

What am I doing wrong?

 

Nothing I think that last update bugged it.

 

AWS changeover lever?

 

I couldn't reproduce the problem, 6A73 works fine for me. Here is a short video, maybe it will help you.