Currently on my lvl 40 Psyker with a Pryomancy build, while sitting in green section of the warp heat bar and even at zero warp heat. I had random warp anomalies spawning on me while channeling Molten Beam.

Skill Perk I am using are Retrograde Psychic Dominion (+75% increase dmg at zero warp heat), Mind Fortress (3% dmg reduction per second to a maximum of 15%) and Psychic Boon (Double the duration of psyker buffs)

I think the problem lies with Perk Retrograde Psychic Dominion and it reading at wrong end of the scale thinking I'm at maximum warp and spawning the anomalies in which in fact I'm sitting at zero warp heat.