solar panels and electricity return

In the political forum, a poster has written this:

"With regard to solar panels and the supposed great take up of the option of creating your own roof top electricity supply, here in Qld the energy suppliers have found that by reversing the flow of electricity in the grids it is leading to critical new problems because the power grid is designed to distribute electricity, not collect it.
Many areas now cannot connect their "surplus" power to the existing grid as the system is collapsing due to power attempting to flow the wrong way in the grid."

Can an electrical engineer here explain this? My simple understanding is that with a 50 cycle alternating-current system, the electrons actually reverse their direction of flow 50 times a second. This seems to be at odds with the item above.

I don't doubt there is a problem, but I suspect it is not as simple as it sounds?