If you haven't already done so, I'd recommend checking the hydraulic fluid in the reservoir. Also, if your records do not reflect that the fluid has been changed, I'd do that also.
We were experiencing similar symptoms along with 'extended' light and buzzer warnings even after I verified they were full up in cooler weather. I changed the fluid in the reservoir and that took care of both problems. I suspect our fluid had never been changed by the PO and there may have been some water contamination...who knows?