arena_lumberyard is really laggy all of a sudden

[Zappy]

Okay, so I'm trying to make a picture (or poster, if you prefer), and the only map I'd find suitable for it would be arena_lumberyard... and while I have made a video in that map before, with really acceptable framerate, now I get like 7-11 frames per second (with ambient occlusion turned off, no spawned models/lights/anything (new session)) when moving the camera around.
Other Team Fortress 2 maps have 30-40 frames per second when doing the exact same thing.
Is this map just super laggy all of a sudden?

If it's of interest to you, I have extracted Team Fortress 2's .vpk files into SourceFilmmaker/game/tf_fix, and edited game/usermod/gameinfo.txt to include tf_fix as a game directory directly above the normal tf that comes with the FilmMaker.
(I have also commented out the workshop paths, as I hate the workshop.)
And I have also installed the Day of Defeat content pack.

I'd really not be able to make this picture(/poster) with such a horrible framerate when just moving the camera around, especially not when looking at the fact that the Translation manipulator and especially the Rotation manipulator make the framerate decrease, no matter the map and such.

[Zappy]

Rushed screencaps of the FilmMaker on arena_lumberyard and ctf_sawmill, all showing the framerate: http://sta.sh/2hk22tvzvv7 (Click the pictures to enlarge them.)
Same session, just different maps. I have tried many Team Fortress 2 maps, and they're all at the 25-40 frames per second framerate, except arena_lumberyard.

[R234]

I tried arena_lumberyard, and I got my usual average of 55-60 fps with AO on. I then grabbed the map from my TF2 directory and stuck it in usermod. Tanks down to about 20-25 O_o

The TF2 version of arena_lunberyard seems to have significant optimization issues, at least in SFM. I bet if you simply deleted it from tf_fix, so as to use the one in tf, you'd get better framerates.

[Zappy]

Looking at the game mode picture of arena_lumberyard, it also seems to be in "spectate" or "waiting for players, since there needs to be more than 1 guy to play Arena maps" mode, as opposed to other maps just putting me straight in the(/a) Blu spawn as a NEED A DISPENS Blu Scout.
Alright, I'll try going with the FilmMaker's version of arena maps.
Oh, and I also tried comparing Team Fortress 2's koth_badlands with arena_badlands in the FilmMaker, to see if the arena_badlands would also lag a lot... And no, it doesn't. It just straight out crashes the FilmMaker.

Edit: And now that I tried with the FilmMaker's own arena_lumberyard, yeah, 30-40 Frames Per Second without Ambient Occlusion, and I can move around if I go to Game mode.
I think the FilmMaker's version of the map is in reality a king of the hill map or something, or possibly even an objective-less map that just has a "static" Control Point prop in the middle of the house thing.