Movie Render Queue Long Sequence Memory Leak – Crashes After 2–3 Hours (UE5.6, 1080p, 64GB RAM)

Community Showcase Film, TV & Animation
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1

Hi everyone,

I’m running into a persistent memory issue with Movie Render Queue when rendering long sequences in UE5.6.

Setup:

  • Unreal Engine 5.6
  • Resolution: 1080p
  • GPU: 16 GB VRAM
  • RAM: 64 GB
  • Output: EXR sequence (sometimes with Cryptomatte/multi-pass)
  • Renderer: Path Tracer
  • OS: Windows 10

Problem:
When I render long sequences (e.g. 1500–2000+ frames) via MRQ, memory usage starts around 50% of my RAM but keeps growing over time until the system runs out of memory and the editor crashes after ~2–3 hours. This happens even if the scene complexity is moderate.

Notes:

  • I have “Flush Grass Streaming” disabled.
  • I keep Texture Streaming enabled and avoid “Flush Streaming Managers”.
  • Warm-up frames are set (32).
  • I tried reducing Temporal/Spatial samples and disabling Cryptomatte, but the memory growth still occurs.
  • Splitting into smaller jobs via command line works fine (memory resets per segment), but I’d like to know if there’s a way to run the full sequence without manual segmentation.

Questions:

  1. Is this a known memory leak issue in MRQ for UE5.6?
  2. Are there additional settings or workarounds that can stop memory from continuously increasing?
  3. Any way to make MRQ automatically “flush” unused resources during a long render without restarting the process?

Thanks in advance for any tips or confirmations.

2

I found that Structured Buffer Memory was pretty high， even reached 250GB

3

Hi !
It used to be a problem so I wouldn’t be shocked if it was back.
I also am experiencing something similar and I was wondering if I was the only one.
Did you by any chance find a good fix aside from restarting the whole thing ?

4

Hi there! I’m having the same problem and apparently it’s related to MRQ and Path Tracer:

No memory leaks after disabling PT.

One way to go around this is by writing a custom Python script that breaks the sequence in junks when submitting via command line (as mentioned by KOINUPENG). My python skills are quiet minimal though so it’s not working properly yet but I can post something once it’s working or someone can have a look and help.

5

Hey there! I might be wrong, but here’s a possible lead - if you’re using any Blender-created assets or third-party models that are very Expensive, your memory might be crashing during rendering. Try to locate the specific asset causing the issue. If you find it, reduce the subdivisions - it could also be things like hair or fur, since UE has its limits on what it can handle.

Another tip: render image frames instead of a full video file. The last frame before the crash might help you see what’s happening in your scene at that exact moment. The goal is to identify the problematic element and either remove or fix it. Cheers!

6

I don’t have any PT enabled nor any expensive models. It’s really a slow bleed over time. I can take traces / memdumps but I find UE hard to memtrace since I’m not familiar with its inner workings.

Albeit my use case is different from the one above since I do plenty of small renders instead of a long one, so the issue might be entierly different altogether. Just giving insights/keeping the subject alive.