I recently acquired a Durst Laborator S-45 (similar to the L-138), and the column spring makes a sort of "thunking" noise when I lower the head for the first time during a given printing session. The action for the head is otherwise smooth. Is this normal?

I'm wondering if this is just the spring readjusting itself, or if there is a mechanical problem somewhere. The table spring makes a similar noise when I lower the table far enough.