There is no really a bug.
Just there is no room to create thermal reliefs for pads 25 and 26.
With your antipad values and the pad sizes, pad 25 creates a 200 mils antipad area that prevents Pcbnew to create a good thermal relief for pad 26, and pad 26 creates a 200 mils antipad area that prevents Pcbnew to create a ggod thermal relief for pad 25.
There is no really a bug.
Just there is no room to create thermal reliefs for pads 25 and 26.
With your antipad values and the pad sizes, pad 25 creates a 200 mils antipad area that prevents Pcbnew to create a good thermal relief for pad 26, and pad 26 creates a 200 mils antipad area that prevents Pcbnew to create a ggod thermal relief for pad 25.