Harddrive being filled up during MRQ render, causing crash

I am rendering a series of simple camera moves for an automotive project. My scene is just a single blueprint that contains the meshes for the car, and then a camera, and a skylight set to an HDRI.

My MRQ is a queue of level sequences, each of which is a single camera move (for ex. moving the camera along the instrument panel, etc)

Notes on car blueprint:

  • built off of the Cinematic Car Rig plugin
  • has many meshes attached inside it
  • ~7mill poly overall
  • several functions that provide controls to the car: turning lights on and off, doors opening, etc. These functions are wired into event tick as well as construction script
  • Set to run construction script in sequencer

Rendering with path tracer. this happens when rendering both 1920x1080 and 3840x2160. Ive been using sample counts like 128 spatial X 8 temporal, etc

When I close the editor, it seems the data is discarded and the harddrive space opens back up.

My questions are:
1 - what is causing this buildup of data, and where is it being stored?

2 - is it related to having many functions on the construction script?

3- is is related to the car being high poly? is there some copy of the geo being made every frame or something that gradually causes a huge buildup of temp data?

4 -how can i prevent this from happening?

Thanks for any insight -this is causing a huge problem in my workflow becuase im unable to set up long-running renders overnight or on another machine, becuase i can’t trust unreal not to fill upthe harddrive and then crash during the render.

Are you rendering videos like mp4s or something? Those do have to be stored temporarily until the job is done. Other than that I don’t think MRQ itself caches anything. Maybe use WinDirStat or something to see where the data is going.