Duplicate frames / messy export in 4K 60FPS

[Graslu00]

When exporting 4K 60FPS footage with both H.264 or H.265 I get duplicated frames on random spots of the exported file.

I've read many forum posts reporting this issue since 2018 at least but the only "fix" I've seen mentioned is to use Software Encoding instead of Hardware Encoding. This isn't really a solution for this issue as that'd extend the render times for literal days, as I have to export hours of 4K 60FPS footage in high bitrate.

Here's an example of the duplicate / repeated frames I'm mentioning (1:08:31): https://youtu.be/X3qJFHGFl8o?t=4111

The source files are recorded with a secondary PC through a capture card in 4K 60FPS 70mbps bitrate.

My PC specs:

CPU: i7 9700k @5.0GHz
GPU: RTX 2080 Ti
RAM: 32GB DDR4 3200MHz
Motherboard: ASUS Prime Z370-A
Capture card: AVerMedia 4K Live Gamer

And here are the export settings:

Any help is appreciated. I've already tried switching GPU drivers to no avail. Worth noting that I have to use Media Encoder to do the exports too, as Premire just throws an error when it's halfway through the export.

[Graslu00]

Testing further... Premiere seems to be adding random previous frames on the video? Here's a comparison shot of the same frame in Premiere (Left) and Vegas (Right).

Vegas is showing the proper frame, Premiere repeats them randomly. This is on a clean project, unedited and origin view, not even in the timeline. These duplicated frames appear on the final render as well.

[Graslu00]

Apparently the issue here was VFR footage, which brings another issue - is there no way for Premiere to handle VFR footage without duplicating past frames? Why does it not just freeze those missing frames to maintain 60FPS like any other editing software?

I can use ffmpeg or other software to convert the files to CFR, but then I'd already be losing quality on the process.

Switching VFR Mode to "Smooth Video Motion" fixes this but creates huge audio delays. Is there really no way around this?