As the title says, whenever I run with a mod that contains any kind of an .obj model of any sorts, my RenderTime rises by 10%. I originally saw this when playing RLCraft and found that Lycanites mobs was causing my frames to drop from 144 to 60 or even 20 at times when in dungeons, but couldn't find the actual source. Finally, I opened up Immersive Engineering which made my frames drop to around 60 just when pulling out the railgun. I remade the model to only include around 40 vertices and only 3 meshes and now the frames drop only by around 20FPS, but there is still a significant stutter.
32GB of RAM, of which 2 to 6 are allocated without any difference.
Everything is on an SSD
Happens on all forge 1.12.2 versions I have tried and no errors in logs.
As a note, I can run Minecraft on highest settings and 24 render distance at 120FPS when not traveling much, so the drops are easily noticeable.