WowAce

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

3.1.5 

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

retail, windows, russian | english

What steps will reproduce the problem?

boss debuffs in dungeons  
Did you try having Grid2 as the only enabled addon and everything else disabled?

no  

Was it working in a previous version? If yes, which was the last good one?

not in midnight  

Do you have an error log of what happened? If you don't see any errors, make sure that error reporting is enabled (`/console scriptErrors 1`) or install [BugSack](https://mods.curse.com/addons/wow/BugSack).

no errors  

Please provide any additional information below.

If I'm using default DispellableByMe with debuff-icons tick besides border tick, I get a way more debuffs that it should be, debuffs that I can't dispell.

for example https://www.wowhead.com/spell=1249014/eclipsing-step

It shows in grid but It's not dispellable.

see, i have non-dispellable debuffs for some reason

https://imgur.com/a/djkyJOc

Dispellable debuffs display is decided by blizzard now. So if some incorrect debuff is displayed is a bug in the game and addons can do little  to fix the issue.

Anyway you can go to the dispellablebyme debuffs filter in Statuses>Debuffs and tick the "Get Dispellable debuffs from blizzard unit frames", this could fix the issue (or not), depending if the bug is affecting the blizzard raid frames too or not.

But as far as i know the dispellable debuffs filters are mostly bugged for most non-healer specs.

As workaround you can create a new debuffs group status, configure the filter to display only "Typed debuffs", set a transparent or black color to the debuffs types you cannot dispell, and assign this debuff group  to the border indicator or some square indicator.