FPS drop on some bosses (slide show)

Hi all.
I have a problem with FPS on bosses like Saurfang, the Lich King, and Professor.
For example - Saurfang. When the battle starts, my FPS drops to 0. And it stabilizes immediately after the mark appears on the second tank. FPS also drops during the release of bists.

https://clips.twitch.tv/SparklingSle...plgLTGFaz8CfOQ

This situation happens on some bosses and for some reason the FPS returns to normal instantly after "bursts".
I tried disabling DBM, WA and TidyPlates on pull. Did not help. Tried lowering graphics settings. Did not help.

I have latest official version of HD client without hard patches.
Please note that this problem is NOT PERMANENT. It appears and disappears from time to time.

Unfortunately, I already know what most people will write - check addons, graphics settings, CPU load….
Thanks in advance for these tips, but they don't provide anything concrete. I'm looking for people who have personally encountered a similar problem and found a solution. Thank you.

Solution: FPS dropped due to the "skada" addon. Changed it to "Details" and the problem disappeared.