As to the grounding in the early 1980s. It may have happened earlier, sorry not sure of dates. There was issues with the Risbridger replenisment rigs. These were used to replenish Hydraulic oil, OM15 aka (H515) and Engine oil, OX38.
If I recall correctly the internal seals were breaking up and being pumped into the systems causing contamination. I believe these were used on other aircraft fleets also caused other aircraft to be grounded whilst the Hydraulic oil and engine oil was drained, flushed and filters replaced.
They were finally replaced with a pump, (not sure what type) directly attached to the oil can.