JMX Monitor Problems

We have configurated about 500 JMX monitors, with a ejecution interval between 5 to 15 min. We made a sitescope sizing
But in some moments We are having alerts storms with results 'n/a' without a really lost of service from the WL or network problems.
Any body know or have this problem?, is a know problem?.
SiteScope is HP SiteScope 11.24.371 64-bit JVM, Build 264
I'll be very grateful if someone can help me.