We have an old Gitzo Rational (Rationelle) PL-5 head which does not lock absolutely solidly in the forward/backward (or in aeronautical terms, pitch). Putting about 30 pounds on the long end of the platform results in it gradually rotating.

We have the exploded parts diagram of a similar model of this head. Unscrewing this handle (see red arrow on attached diagram) does not show any missing parts. This threaded handle/steel rod has a rounded end that is supposed to lock the head and this seems undamaged. Exchanging this rod to the other side of the head so that it extends forward similarly does not lock the head solidly.

Any suggestions on how to fix this? One photographer said there is a fiber bushing that can wear out. However unscrewing the side to side tilt handle (D1270.08 in the exploded parts diagram) does not let us further disassemble the head.

Thanks in advance.
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