Describe the bug
Nameplate timer on mob seems to have frozen. Unsure if Core related or module related.

Do you have an error log of what happened?
Skittering Breach, Renilash Beckons.zip

Screenshots

Did you try having DeadlyBossMods as the only enabled addon and everything else (especially something like ElvUI) disabled?
Nope

Which version of DeadlyBossMods are you using?
Core 11.0.39-23 alpha
Dungeons r179-6 alpha

They weren't CCed in any way, but good to know, thank you.

Frozen just means they didn't cast it when it came off CD. that's designed behavior. maybe they were chain stunned or something else.