If you can please get a video of this that would be great. I will look into it and place it into recent reports if I can repro this before you add a video. Thanks!

I am going to move this to recent reports as I added the issue for frost proton slowing chrome enemies, If you manage to get a video of Viper fangs bubbling chrome enemies please put in another bug with video

Guess it needs special conditions but can't get which exactly.
Did some runs yesterday but still can't buble them up.
Sure if i'll do this again i'll record and try to tell you special conditions too.
(if it wasn't fixed for so short time o_O)

All I've got now is this screenshot :

I'll try more and if i'll find reason or at least more datails i'll create new thread
On screenshot - it's spawned by Healer mob skeletons.

i think this is just a case of the summoned "extra" enemies are not chromed, but it seems like most the rest of the mobs on the map are not able to be "bubbled"

I thought chrome enemies just could not be stunned or knocked up. I am pretty sure slowed enemies is allowed in Chrome incursion. 

Also, the only enemies I have seen bubbled up are skeletons that are spawned from the dark mage. Those skeletons don't look Chrome. I figured since they were not Chrome, they were game for bubbling.

Yep you was right at both things :)
1.Bubling summoned skeletons - intended.
2.Slow...if it's intended - frost should slow them too,as i seen - it doesn't now)

So...first of all we should know - should slow be possible or not.
Thought not cause frost slow doesn't work...

If it should slow - here's frost bug
If shouldn't - proton.

After few more expirements:
Guess we can close this thread cause of:
1.Frost works too,but here's almost no difference between serenity and serenity+frost.
Looks like intended and ok.
2.Protons slow them too and it doesn't conflict with map rules.

Guess oil slow works too.

P.s. sorry about it :D