Aggregation/calc "sometimes" does not roll up value to the parent member

We are on 11.1.2.4 and have had this version with the br in question running with no issue for years.

over the past few months, we have noted that the calc has completed with no errors, but the value has not been aggregated to the final parent member.

Running the script again and then it updates as expected.

Most of the time this calc does aggregate the whole way, but we have been finding when it has run over the weekend it 'sometimes' has not rolled the whole way up.

Work around is to run it twice when this happens, however this is a long running rule and cuts into business time when this has to be done.