Sadly, this is an endemic and widely reported issue on all Pi models. If you do a web search on this problem there is no, single, obvious fix.
I realize this post is pretty unhelpful

other than to assure you that you are not alone.
My recommendation is to Google the problem and try all the various solutions. Remember that if you upgrade the kernel you will need to recompile some of the G2-specific software (there was just another thread on this).