@SavageCDN I am definitely counting virtual groups, I've set the spawn radius to zero so that the AI will never be spawned into the world while I am testing. I've also set the number of attacking groups to 100, so that should not be an issue.
Looking at the debug, with one placement module with 1200 units, the largest group number I see is e8. Adding in a second placement module with 100 units, the largest group number I see is e16. Placing down another 100 unit placement module and the largest group number I see is e24. The TAOR is set up correctly, they are only being placed within the TAOR I designated.
I tried increasing the TAOR coverage, and with that more units spawned in. Nowhere near 1200, but still more units. It's like it can only spawn in so many groups into a given area, and if it can't spawn anymore, then it just stops placing units.
@HeroesandvillainsOS Thanks for the suggestion. I may end up doing that so I can get more fine control over what units spawn and such, but I would like to see if I can sort this issue out. If it is a bug, then it would be good to let the developers know, and if it is an issue with the way I'm setting it up, it may be worth adding a line somewhere in the wiki to clarify how to make sure the placement modules place down more units.