WowAce

What version of Grid2  are you using (Version is displayed in General/About Tab) ?

v2.8.59 

What game client version, classic or retail, windows or mac and language are you using ?

Retail 

What steps will reproduce the problem?

Hard to say, sometime I would run M+ dungeons and none of the raid debuffs would show up. 

 
Did you try having Grid2 as the only enabled addon and everything else disabled?

No

Please provide any additional information below.

 Sometime raid debuffs would not show up at all throughout the dungeons. One thing that happened which was really weird was that I went through Dawnbreaker +10 and did not see any of the raid debuffs at all for the entire run. Then we cleared the dungeon and after the M+ is over, the permanent debuff Radiant Light finally showed up on my grid2 frame.

/reload did not solve the issue, and I for sure had both M+ Dungeons extra module and TWW module enabled. 

Disable another addons specially weakauras that can change or add things to the grid2 unitframes.

Enable console errors and check if some lua error is happening, typing in chat:

/console scriptErrors 1

Goto general/about Tab/Debug section and click/enable "Grid2RaidDebuffs".

Then when the issue is happening after reloading the UI, watch for one or several messsages in chat with a format like:

Grid2: DEBUG Grid2_Grid2RaidDebuffs Zone[Zone Name] C_MapID[????] EjID[????] mapID[????] Status (raid-debuffs): ? raid debuffs loaded from [?]

And post these chat messaged here, you can post the message displayed just when you enter the instance too (not only when the ui is reloaded) to compare if the game is reporting a different/wrong zone in some dungeon subsection.