I recently bought a volvo ECR88 second hand, and I knew it had a few issues when I bought it. Have worked out all except for this one. The boom likes to lock up and not go down occasonaly, if you raise it a little more and then go down quick it will go down,(fine as long as you are not all the way up) but if you just push down on the lever it will labor the engine. It seems to happen more often when you have a full bucket and the stick all the way extended (more weight on it).