BOOST causing graphing gaps

[Conz]

After updating my cacti from 0.8.7 to the latest last week and adding a few plugins (boost/monitor/settings/weathermap/thold) I noticed today that since then there are intermittent 20 minute gaps in the graphs. (the boost timeout is set to 20 minutes)
These gaps seem to correspond to the period where the boost plugin is doing its 'update all RRD's'.
I'm only monitoring 15 hosts right now and the cacti server is a 2 cpu VM that did not have any issues before installing boost.

I'm guessing its so busy with the 2 hourly update that somehow it doesn't get around to running the actual probing .. but that seems a bit odd.

Anyone know what might be going on ?