Export Issue: Different Source Framerates Leads to Stuttering
I am using Hitfilm to create cinema montages, each comprising of multiple films. When exporting to the YouTube 1080p HD preset, I found in the final mp4 that the footage from select films was consistently losing frames while others were being spared. After some experimentation, it became clear that the source footage of 23.976 fps was processing appropriately while the other footage, running at 24 fps and above, were the only ones suffering from this frame drop effect. I performed a sort of bandage solution by converting all of the footage with the inappropriate frame rates into the proper 23.976, and it worked, but it causes audio sync issues, increases storage requirements, and therefore can lead to more problems down the line.
I'm wondering if there is a way to process films of different frame rates without resorting to any converting, or otherwise if there is a way to convert video to a different frame rate without causing audio de-sync issues.