Standing by to be corrected, but I think it was the wrong anti-seize compound/thread lubricant applied to the m/r hub nut threads. I think it reacted with the xmsn oil vapour and attacked the threads causing them to fail.
TRC, your thinking of the accident that involved a different Alouette II, a 318 not a 3130 like G-FILM. It was
G-AWAP that had heavy corrosion on it's Jesus-bolt but it had not been checked in 4 years due to poor maintenance. Indeed the the xmsn oil vapour did react with the non specified lubricant but if the maintenance schedule has been adhered to the corrosion would have been identified. Look at how horrifyingly corroded the threads are in the highlighted report!!
G-FILM was involved in a fatal wirestrike whilst filming in May '82.
Taken from griffin-helicopters:
The helicopter was engaged in filming work & the wreckage was found on 23 May. The A/C was in transit from Grobnik A/D to a private landing site at O'Malley's field near Boljun. The A/C appears to have struck three lowest wires of a 6-wire telephone system strung between poles on either side of a valley. One of the wires was found to be wrapped around the rotor head. The helicopter impacted with a rocky outcrop & came to rest on the valley floor. The wires would not have been visible against a dark backgrond. CAA closure: See YUGOSLAV CAA accident report dated BELGRADE JUNE 82. NO FURTHER CAA ACTION.
Unfortunately I'm unable to find anything else related to G-FILM's accident.