Choppy video even with 'Lossless' settings?

I’m using Blender 2.82’s Video Editing pane to create a video from a series of images (also generated in Blender).

No matter what settings I use, I am unable to create a consistently fluid video. Although some sections are smooth, there will always be bits that are choppy (seemingly at random times).

Image sequence:

• 5000 images
• PNG format, generated by Blender
• Dimensions: 1920 x 1080
• Size: ~3.68 MB each
• Bit depth 25
• Compression: 15%

Output settings:

• Frame Rate: 24 fps
• File Format: FFmpeg video
• Container: Matroska
• Video Codec: H.264
• Output quality: Perceptually lossless
• Encoding Speed: Slowest

What’s more, despite the choppiness, the output file is huge (2 GB for a 3:22 minute video).

Any advice on generating a smooth video? What would be an expected file size? Thanks.