This is the first I've heard of Davinci Resolve. That looks like a fantastic app! The sound editing alone looks amazing. Probably the coolest free app giveaway since free ProTools. Unfortunately it's only for 10.15 and up so it won't run on my Mac. I seem to have two machines that were from this hinterland time period where nothing Apple was backward compatible enough to work and QuickTime had too many of it's functions amputated. Guess I can mess with Blender for the time being. Still not a fan of its interface.
Invest in a pc and get rid of these obstacles, and you will also get access to plugins for lightwave not available in the Mac platform and other stuff along with it.
use mac for things it otherwise does good, but don´t rely on it.
Or ..use blender to convert the image sequences as I linked with the video, if mac has an issue with that too, then you have an issue with a platform you can´t rely on.
Edit..or try the suggestions by Markc.
Davinci resolve is sweet, fast to edit and scrub videos back and forth, it has limited filters though which requires pro versions, generally for some stuff I would prefer Adobe premiere and after effects, easier to replace clips, save out to gif anims, text preset animations etc, but when the economics are tough today, and a prescription renewal would cost me too much, I decided to end the Adobe Prescription and go for the Free davinci resolve version for now at least.
Fusion is the module you switch to for doing more advanced stuff with masking, tracking, vector animation and much much more, similar to after effects, while the davinci resolve module is similar to adobe premier for editing, color grading, simpler titling etc.