I left my computer alone for a few hours. When I left, there was ~100GB of free space in the /Home directory on my laptop. When I came back there was zero free space. I moved a couple of large files to an external drive. Dolphin showed there was 2.5 GB free space, so I decided to move a few more files to the external drive. As I was moving them, Dolphin was showing less and less free space available! In less than 5 minutes, I watched it go from 2.5GB free, down to ~850MB. After rebooting the laptop, it showed 100GB of free space once again. This happened repeatedly. Eventually, I discovered a file called ".xsessions-errors" was the culprit and that this only happened when running Kodi.
I suggest to report it to Kodi authors. You might need to report which line is repeated in debug output.
It happened again yesterday on a fresh install of Neon. Not sure if it is only with Kodi because there are other bug reports about this same problem from other users running different apps. I posted this problem on the KDE Facebook page in November and the solution was to change the compositor from the default (OpenGL 2.0) to xrender.