[askycobra]

This is for my 1969 337D. In my case the right brake would go flat and the left would stay up. As in an earlier response the problem was traced to fluid seeping through the parking brake control. The right master is higher than the left and fluid was gravity flowing through the (unset) parking brake control and seeping out the top of the left master and puddled in the belly. A couple of O-rings and the problem was solved with a parking brake rebuild.