FPS drop in regular interval

Hello everyone!

I’ve been struggling for several hours with strange problem.
I have small lag in editor ideally every 5 seconds.


I tried to figure it out with profiler:

On the yellow (Threads) and pink (GPU) only thing which I can read is that CPU Stall / wait for something.

Frame before the drop looks like this (and I think that it can be the clue what’s going on):

So the “Update Buffer RT” is happening - anybody knows what that means?

I can also see that in resource manager. On the graphic card tab the small tick shows in copy section.

I guess that it is connected with vram memory? It wasn’t on the same project before. The scene is quite big. Is that possible that the too big lightmaps are reason? I have a few hundred MB of them in total.

I saw similar old issues:

but it’s nothing like this. :frowning:

Thanks for any help!