t140 left track won't turn forward until hyd sys warms

I have a 2005 takeuchi t140 with 2100 hrs. After startup, the right track will not run forward until the hydraulic system warms up. We have to drive the machine around backwards for sometimes 20 mins before it frees up. The machine runs strong after it warms. This problem showed itself over a year ago and has gradually gotten worse, but it always eventually operates correctly. The fluid and filter has been changed. A service manual or insight on what the problem might be would greatly be appreciated.
Thanks,
JM

t140 left track won't turn forward until hyd sys warms