Problems importing MOV (PNG codec) files from ProductionCrate

I’m editing a short film in kdenlive and am using several VFX from ProductionCrate, all downloaded as MOV (PNG code ) files. While some of the videos import and play beautifully in that format, with the alpha channels keying automatically, others either won’t play at all, won’t key properly (the background appears black, forcing me to chroma key to insert the image, which often looks terrible) or, in the case of some laser effects, the edge glow bleeds everywhere and it looks like a splatter painting.

I can’t figure out why the footage is importing so inconsistently. All the videos are all the same file format and should all play the same in Kdenlive, but there seems to be no way to predict which clips will work and which won’t, or how to fix the issues.

I’ve written to ProductionCrate to see if they have any thoughts, but I can’t be the only person who’s had this problem. Any thoughts or suggestions would be greatly appreciated. Thanks!