I'm not really sure to be honest. I know pretty much nothing about OOS issues. Perhaps running a debug DLL and taking note of any asserts that come up when the Infernals are created will point in the right direction?
We decided to destroy the Infernals. We were the ones who summoned them and they were helping us with destroying all non Ashen Veil civilizations, but dealing with an OOS error every three turns or so was not worth it. We had a last OOS a few turns after we killed them, and the game has been running smoothly since then...
Once that I finish with some modcomp merging I'll try to learn about OOS debugging and give debugging this issue a shot using only More Naval AI. Although unlikely (they don't alter any specific civilization), it might be possible that one of the modcomps I use is causing this.
It would be quite helpful if someone else could confirm that he gets OOS errors as soon as the Infernals are summoned with either 1.8.5-beta or 2.0-beta. Thanks!