Using 5.1.2 on Win.
I’m doing a 4 layer PCB and there are some driver chips on the Front layer. The Front layer zone extends across the entire PCB. There are lots of other pins which are GND and are appropriately connected with thermal relief connections. For some reason, the fill does NOT get pins 4,6 9 (as shown in attached screen grab).
PCBnew is aware of the GND connection as it draws ratsnest from these pins to nearby GND stitching. I had to install the traces shown to actually ground the pins.