Q: Problem with other storage

OS X: What is "other" space in About This Mac? - Apple Support

Two things about Other

1. When all is well Other is simply any other file that doesn’t belong to any of the other categories listed
2. Unfortunately it doesn’t take much for the Spotlight Index to get munged. When it does files that actually do belong to some other category (such as Audio or Apps) will get tagged as other instead. Actually I think saying it gets tagged as Other is a misnomer. I think it may be that the lack of a tag is what gets it labeled as Other in the listing

It is possible (sometimes with great difficulty) to reindex files so Spotlight tags files properly. I belong to the group of people who ignore Spotlight so I don’t bother. This article: Spotlight: How to re-index folders or volumes - Apple Support describes how to reindex and sometimes it actually works just this easily. Other times it is necessary to jump through a few more hoops.