Expandable grid - rows under expanded row are messed up

There seems to be an issue using Expandable Grid - whereby when you expand one of the rows, the rows underneath the expanded row seem to lose their formatting and are just all joined up.....

I have taken a sceenshot which you can see here: (Note I've covered some data but you can see the issue anyway)

Is this a known issue, if so is it being fixed or is there a work around please?

Note I am on rc-19.