MQDH Performance Analyzer flags VRC Perf.1 periodically

Hi all, I'm testing my app with the Performance Analyzer included in MQDH. The problem is that it flags periodically VRC Perf.1, even if the fps are stable in the app (I know that becouse I measure fps also with OVR Metric Tool and the graph is stable on 90 fps
Instead the graph produced from the Performance Analyzer is a sort of sawtooth wave, as illustrate from the following pic, that oscillate from 90 to 17 (or another low value).
It appears somehow releated with rendered layers. Inded I see that when the wrong drop is reported, the 'rendered layers' is zero.

Any help please ? I fear the reviewers use this tool 😕 Tnx very much