Ghost Splinters - Unable to capture resource node

Last night when I sent a small army to capture the radioactive resource node, after the splinters were cleared, the node stopped capturing after a couple of ticks as if another had spawned to protect it, although none were to be seen.

All of my units were aiming at a single spot, but not firing, units that I had ordered to attack-move passed the spot stopped and joined in the waiting game as if they were all trying desperately to get a target location of a unit that had buried itself underground.

I tried building smarties around the area, but they were unable to get a target lock either.

I have to say, it is quite a bit more challenging playing without radioactives. I had to push forward and capture the enemies radioactive node instead.