compression pin to yoke guide hole interface
Also, check the compression pin to yoke guide hole interface. Have you been lubricating on a regular basis with white lithium grease or similar? Check for any galling between the steel parts if they were run dry very long. Check for any burr on the compression pin or yoke hole. The return force is only a hundred pounds force or so, whereas the hydraulic force driving the pin out is up to 3K.
Another cautionary note: The yoke holes are reamed a thou or so larger by the manufacturers, over the .375 diameter pin, and in my experience over time the mfg might not change out the reamer and thus the holes can get very close clearance to the pin diameter. There still could be an issue with the unit, I'm just pointing out other factors maybe not considered.
JDA makes a good point. Adequate lubrication, on the order of 6-8 drops per several hours of continuous use, should be added to the intensifier. Otherwise, the o-ring in the intensifier can get dry and grabby, and start to deteriorate.