1. Download mission file (works fine with mods/ vanilla, same results)
2. Play scenario in eden / on dedicated server. Bots will spawn after 15 seconds.
3. Wait until bot counter reaches 1000-2000 (best way to force it to happen early, it could take some time. Just leave game with camera pointing at every bot. No worries, only spawn max 40 bots at same time. I think this could be skipped to just 100-200 bots and fps should go to lower values too.)
4. Watch your fps goes from 120 at start, 60 from spawning bots to 20-40 after couple of minutes
5. Stop spawning script when you see 20-30 fps (in my case, depends on PC), delete every bot from map with this command (exec it on server):

testing = false;
{deleteVehicle _x}forEach allDeadMen;
{deleteVehicle _x}forEach vehicles;
{deleteVehicle _x}forEach allUnits;

6. Watch your fps stay at similar fps that was with bots, and goes to lower values with each minute.
7. If you have “profiling - Performance Profiling Build” enabled, use command:

diag_captureFrame 24;
and see what causes it.

8. After copule of minutes of doing nothing, fps could go back to original state (120fps) or just slightly lower, 100fps in my case. If you wait couple minutes more, they should go back to original state (120fps my case).

I think that everyone encounter it, because it happened after every firefight. Fps suddenly drops, and goes down with every minute. Sometimes after some time it goes back to normal fps, or “just enough”.