I've found the frame dropping a bit of a mystery. Maybe your experience and mine can help resolve it. I spent a whole day shooting a soccer tourney and had zero frame drops in over an hour of footage. I shot some indoor footage and had frame drops on almost every clip. Both were shot 4K and 24 fps. I'm using a Samsung EVO+ SD card. Logic says the only difference is that one was relatively low light but I can't imagine how that would ever cause frame drops. I've decided to get a faster SD card to see if that helps but would be interested if what your experience is. Are you always having the problem or under what conditions?
Yes, I also find lower light drops more frames. I use the Lexar 1000x, but the card doesn't seem to make a difference, same performance with supplied Lexar 633x card