I was doing some performance tests using TNTs and I noticed that sometimes the primed_tnt entity will fail to finish the animation and explode if it tries to explode outside of the entity render distance (that is, after it fades out). Instead, it'll create an big white cuboid entity.

Steps to reproduce:
1- use the /fill command to fill an area with TNTs
2- Explode the TNTs
3-After the explosion is over, go to adjacent areas to update the TNTs that were launched by the explosion (flying close to the ground increased the chances of finding one for me)
4- The White Cuboid entity will likely be falling when you spot it

P.S.: I actually found a report similar to mine but it was tagged as imcomplete because the guy who made it didn't explain what was happening so I decided to make a more detailed one