Premier Elements -- matching different years, for lossless merging

I've been using 2021 Premier Elements for years, now trying Elements 2025, want to get newly saved mp4(2025) files to match parameters of older mp4(2021) files, close enough for high-speed lossless merging in Bandicut. I've matched frame size, frame rate, keyframe rate, and audio traits; and, I’ve tried both Constant Bitrate, and Variable Bitrate. But, none of those have been good enough for Bandicut, which keeps saying, “no, if you want to merge those two mp4 files together, you will have to use slow frame-by-frame encoding, and that will be lossy.” How many more parameters do I need to align, and what are they? I’m using a Windows 10 system, to create 1080p files, with a target bitrate of 11 Mbps.