Kato HD 900 SEV slow operaion

Hi all I need some help with a Kato HD 900SEV digger S/n 900514sw
the machine has pilot operated controls for the main attachments and uses cables to operate the travel spools
the problem is when machine warms up the functions on the left hand joystick go slow. operating the right hand joystick improves the slow functions. i suspect the pump signal system but do not know how it operates as the pilot lines go directly to the main control valve .there also appears to be no pilot pump as such....

Kato HD 900 SEV slow operaion

Kato HD 900 SEV slow operaion