Actually just about any player that plays DVDs can handle Blu Ray. I think your problem is more hardware related. You have a heck of a high video bitrate that needs to do 2 things. 1st it needs to be reassembled. Even though there is an enormous amount of data stored on a Blu Ray disk, it's still compressed and Blu Ray disk tend to be produced with large amounts of data dedicated to multi track audio. Leawo player is a free player that claims to be optimised Blu Ray playback.
It all comes down to having enough CPU cycles available to decode UHD video in real time. Players can aid in cache memory management. If you look at the size of the stream feeding the player, scenes with a lot of movement and color take a whole lot of bandwidth while no movement or blank scenes use very little. The ability of a player to "look forward" and cache the raw video into fast ram qued up for deoding. Compressed video is a black art and changes somewhat depending on the codec and the definition of the video.
