Issue explained, see below.

Bug overview description. You cannot exclude more than 1 file type in your search (for example "animated -type:webm -type:swf"). Attempting to do so will only exclude the last file type given.
What part(s) of the site page(s) are affected? Search
What is the expected behavior? In the example, that neither webm files nor swf files are included in the search result.
What actual behavior is given instead? Only swf files are excluded. Attempting to search for "animated -type:swf -type:webm" will include swf files but exclude webm files.
Time of incident (if applicable). N/A
Can you reproduce the bug every time? Yes
What steps did you take to replicate this bug? Attempt to exclude more than 1 file type from any search.
Errors or other messages returned (if any). No error messages are displayed.