It is actually happening on all videos, not just 60fps. opera://media-internals report this:
debug ISO-BMFF container metadata for video frame indicates that the frame is a keyframe, but the video frame contents indicate the opposite
I think this error is related to the frame drop. I installed Opera through Manjaro software center (pamac). opera-ffmpeg-codecs 78.0.3904.108-1 installed with it.