Hello,
The MediaInfo tool embedded withing FITS only supports OSX, Windows, and RedHat. Other versions of Linux will likely result in the FITS code skipping the use of this tool.
Unfortunately, the developers of FITS have no experience with ResourceSpace. However, the version of PHP you are using likely does not have any impact on FITS as it does not use PHP in any way.
Also, curious what types of A/V files you are processing. What are the file types and file extensions?
Thanks,
The FITS development team