R3483 failing with "EventRule : Business Function MRPMultiplePlantLoadAndPlan at line 86 for Event 1

Hello All,

I am having problems getting R3483 to run consistently in our PY environment (we don't currently run MRP in live but want / need to) and wonder whether anyone else out there has the same battle scars and can help. Sometimes it runs to completion, other times it ends in error always with the same message as above. I am reasonably confident of my item set up and R3483 configuration:

     1. Only 2 branch plants being used. In use for years. Branch plant constants exist.

     2. Not exceeding the maximum number of time series buckets. Planning horizon periods are 0D, 12W, 10M. Forecast consumption period end dates match planning horizon period end dates. 22 + 2 past due periods are all that are being generated.