Blank sub page after ee3 upgrade

I have done quite a bit of debugging to try and figure out whats wrong with this page.

I have a channel entries tag that loads 3 divs per entry that are roughly the same size. There are 312 entries when i load a single div per card, max mem usage is around 28mb. if I increase that to 2 divs, the page turns into a blank screen (although my debug tool still appears. its running before the controller im pretty sure) the memory usage goes up to 33mb (temporary php cap is 512mb, for testing purposes)

the only thing i notice thats different is that when the page does not load, EE does nto process any sub templates. I cannot figure out why this is. It doesnt matter which divs I choose, any 1 will load, and any >1 will fail. The divs do not contain any addon hooks, and dont contain any additional scripts. they are pretty much flat html with some ee variables in them (ie. title, or url_title)