Please help: TechMon patchy metrics in 7.1 SP8

Hello Experts,

I'm wondering if anybody come accross an issue I have in Technical Monitoring of SOLMAN 7.1, SP08.

Some metrics (not all) for CRM managed system are patchy: they dissapear for a while and then reporting OK again:

For the time they dissapear, the metrics are grey in TechMon, and then they are reporting OK (till a next time when they dissapear):

Any idea what could be a reason for such issue?

Your help will be really appreciated.

Thanks!

MM