Just checking the obvious: There is enough hydraulic fluid in the reservoir?
One of the known weak points of the DL1000 is the seal on the slave piston. Being in the front sprocket area, this is subjected to all sorts of crud off the chain, and at some point in time it will start leaking, causing a gradual loss of hydraulic fluid. The only solution to this is to take the slave apart, clean the cylinder and the piston, and replace the seal. In fact, in my case I found the cylinder wall to be pitted beyond repair, so I replaced the whole assembly.
I also found that my diaphragm had squeezed itself into the reservoir, raising the apparent fluid level to within the sight window. So I thought I had plenty fluid, while in fact the reservoir was nearly empty.