Quicktime H.264 Render Hangs at ~Frame 25, then Fails with "Memory Is Full" Quicktime Error

Hey all, I’ve searched the forums and have found several threads discussing this issue over the years, but none have a posted solution. I really hope my post can be the one to finally get an answer.

I am on Harmony 20 Premium. I recently moved to an entirely new PC, with Windows 11. Ever since, I’ve been unable to export via Write Nodes or Export > Movie, using Quicktime set to H.264 in Movie Options. I cannot budge from this codec selection for the purposes of the production I’m working on.

When rendering, the progress hangs briefly at about 25 frames, then continues on to ultimately fail. Most of the time, it gives me the QuickTime Memory Full (“-108”) error. Whether it gives me the error or not, it produces an MOV that cannot be opened.

I ran Harmony as Admin, and the log spits out the following at the same moment that the render hangs:

Failed to read in pipe with error (size = 4):
(997) ‘Overlapped I/O operation is in progress.’
Failed to write in pipe with error:
(232) ‘The pipe is being closed.’

I have 32GB of RAM, a Ryzen 7950X3D, and a RTX 3080. I’ve tried every conceivable combo of permitting more or less RAM in the Render page of the Harmony prefs. I’ve tried enabling Harmony’s disk cache and giving it 20GB to work with. I’ve tried limiting the number of CPU threads Harmony can use. I’ve tried disabling GPU acceleration. I’ve tried increasing my Page File size. I tried opening my file in Safe Mode to see if some random service is causing issues, but Harmony fails to boot. I’ve reinstalled Harmony, Quicktime, and the OpenH.264 codec. I’m out of ideas.

Please help! Thanks in advance. Happy to provide any additional info you may need.

Edit to add: I’m working at 1080p. Kicking the Scene resolution down to 720p allows me to render, but this isn’t a real solution.