Try loosening the screw on the side coverplate 3 to 4 turns. The side cover has a rubber gasket. You may have excessively tightened the screws, causing the gasket to overcompress. If this happens, the inner part of the side cover will lean against one or all the control pinions, causing them to stick.
Replace the rubber gasket with a new one. Any Bosch diesel service shop will have it.