CS:GO max rounds causes fps drop

[truemax]

So yesterday i was training until i opened scoreboard and my fps went to 20-30
If scoreboard is closed i get 200+-

So tracked lag to mp_maxrounds. If i set maxrounds to 300 is fine, but if i set over 1k, my fps goes to 20-30.
Anyone experienced it?

EDIT

Upon googling around ye it seems other people are affected too

[jiyeon]

Are you using the Panorama UI or the old legacy/scaleform UI?