Some chipsets fail to upconvert 720p24 properly. My Oppo BDP-93 (Marvell Qdeo 88DE2750 chipset) used to upconvert to 1080p24, but then there was a firmware update to fix a colorspace bug and 720p24 now goes to 1080p60 just like yours. I’m afraid in my case the fix is a new player, since it’s long out of support. What’s more annoying to me is that the 480i NTSC decoding went to crap at the same time too, in a much worse way. So it’s very possible the hardware itself is at fault, but I don’t know your model specifically. If only HDMI supported 720p24, then you could just pass it as-is and let the display handle the upconversion. Argh.

Hey, I bought a set of TR47 discs from some guy something like 15 years ago now. I didn’t know either. Live and learn.