Infested Eximus units are immune to Beam(?) weapon damage

[Karonuva]

Not entirely sure if there are more weapons affected, possibly could just be beam related. Brief testing in the simulacrum to pinpoint some of the eximi and weapons affected and it seems a bit random, however most if not all Ancient, Boiler, Brood Mother, and both Mutalist Moas are immune to Quanta Vandal damage (modded for Radiation), while a few Crawler Eximus units are immune to Glaxion damage.
Would require individual testing on each type of eximus of each enemy with each weapon to know for certain.

Thank you

UPDATE: This seems to affect other enemies as well, Corpus Ospreys and Security Cameras are also immune to Quanta Vandal damage.

Edited October 26, 2018 by DjAirsurfer
added info