[BUG] Graphics become really choppy and laggy on Level 18

I've played Xonotic for years, starting with the older version 1.8.1 which never presented me with the issues I am facing with this newest version 0.8.2.
I have had no problem with the new version until I reached level 18 "oilRig" Deathmatch, in which my input lags less than 1 second very constantly, rendering gameplay virtually impossible. using weapons, jumping and moving is triggering significant lag. I checked my graphics settings in both the game by lowering the graphics, as well as lowering the settings in my Nvidia control centre, still to no avail.
I ruled out graphics issues by playing all older versions of Xonotic starting from 0.1.0.
I know this isn't because of my rig and it must be a bug of some sorts in this new release, since all other levels before level 18 work just fine with graphics settings on MAX, with the exception of a half second freeze during gameplay on some of the lower levels.
I will be playing the older version until this bug is found and fixed.
It is definitely the game and not my PC since all the older games work and the issue starts at level 18 playing version 0.8.2.
I previously posted under a similar name about this issue possibly being due to the new weapon models, and still no resolve.
I am starting to fear this fantastic game is being butchered. But I have a gut feeling this is some bug that needs to be patched.
Many thanks.
Dedicated Player

The engine wasn't made for open maps like this, new weapon models might have hurt perf a bit too and i also think bot AI has gotten a lot better and more demanding (for sure in autobuild/git but i think some of those changes are in 0.8.2 already).

As for the fix, oilrig is most likely gonna be removed from 0.8.3, long term we hope to switch engines and languages to avoid these limitations. (Gradually, no big rewrites to calm down people who see "rewrite" and wanna scream "BAD IDEA" at the screen)