Undispellable Debuffs are being Dispelled

The stun itself is a normal stun, however the stunned unit having plague is meant to prevent a dispel.
Plague remains as expected until they heal to full health

I encountered the 5th brother issue in conquest
My Team: Talzin lead - Daka - Merrin - Ventress - Zombie
Their Team: GI lead - 5th Brother - (I do not recall the rest of the toons on the Inq nodes)
I would have 2 or 3 of the enemies stunned and with plague, 5th brother would take a turn and use a special ability. Stun would be dispelled from all of his allies whilst these enemies would still be plagued.

I have witnessed the Jabba issue many times, usually whilst doing NS vs Jabba in GAC
My Team: Talzin lead - Daka - Merrin - Ventress - Initiate
Their Team Jabba lead - Krrsantan - Boushh - Lando - Embo
All enemies including Krrsantan would be inflicted with Plague, I would use Daka Basic, Ventress Basic or Merrin Special 2 on Krr and they would be stunned. Jabba would then dispel the stun and grant him Offence up, despite him having Plague.

Additionally at 5:34 in this video from The Playbook;

https://m.youtube.com/watch?v=4PgIeLDGHZY&t=441s

we see Old Daka use her basic, land the stun on Krrsantan then Jabba immediately dispels it and grants Krrsantan offence up

EA_Gunner​ he is saying that when Rex takes his turns the datacron is dispelling debuffs that would not be normally dispellable. So the datacron sees any debuff that exists with the stun/daze category tag and will dispel it, whether or not the debuff is actually dispellable. So units who have Plague on them cannot have their debuffs dispelled until the plague is gone, but the datacron is still able to dispel stun from units that are plagued, which should not be allowed. The datacron has also been seen dispelling the locked Daze effects from GL Leia's first special. The locked daze should not be dispellable, but when Rex takes a turn he dispels it and applies the protection disruption. 

An easier way to see this is to run it vs a team with Hondo Ohnaka and his GAC omicron active. He will captive someone, and the captive is tagged as a stun effect, and when Rex takes his turn you will see the Captive debuff is cleansed, enemies are inflicted with protection disruption AND the enemy Hondo will get his extra 10 ransom stacks immediately even though the captive unit has not gotten enough buffs yet, none of which should be happening. 

That said, the FDC is about to dust anyway in 5 days and this is probably a low priority at this point

Scorch start of battle Locked DoTs are being dispelled by General Kenobi
(The Negotiator will convert the DoTs to HoTs)

Flagged to studio

Not sure what you mean here
Fifth Brother and Jabba both dispel Stun from Plagued allies
(5th Brother Patience dispels Stun from Inq allies)
(Jabba's The Illustrious automatically dispels Stun from HC allies)

Do you mean they dispel "Plague" from Nightsisters? Or locked Stun? 
Can you tell me against what teams you have observed this? 

Rex Cron dispels locked Daze / Stun / AB from allies
(Notably dispelling Hondo's locked Daze he applies to Sith enemies)

No issues in our tests