evalMetrics returns different results by changing the interval

I do evalMetrics on the expression:

“sum(eval(‘HOUR’, (available(” + consumptionExpr + “) == 100)))”

where the consumptionExpr is a compound metrics

“consumptionExpr = “avg(eval(‘MONTH’, available(BES) > 0)) ? BES: ECI”

When I evalMetrics on interval=‘HOUR’, all data are available, but passing interval=‘MONTH’ returns all data missing.

My server is “7.8.8.76-1"