Steps:
1. Open small project attached by QA (just a scene with some static objects)
2. Bake occlusion culling, save scene
3. Look at no. of files in Library
4. Move some objects and bake occlusion culling again, save scene
5. Look at no. of files in Library
6. Repeat step 4-5 and you will see that the no. files increase a lot and never decrease

Reproducible in: 2019.2.0a6

Take any project with a relatively large scene and take a look at the number of files and the size of the Library folder. Bake Occlusion Culling for the scene and save it. Compare the number of files in the Library folder and their size with the previous numbers.

Move some objects around and rebake occlusion. Clear the baked data and rebake occlusion. Notice that the number of files and the total disk space they take keeps growing and growing at a very fast pace and under no circumstance is it getting lower (meaning we never clear up old data).

This is causing issues on some hard drives formatted as NTFS (like in the case of this bug), where the Library folder has more than 1 million files taking 10 GB. Operating systems don't like that very mush, so we need to find some way of cleaning up the Library folder where possible. (maybe have a Clear cache option similar to the one for Lightmapping)