The 6.8 release tightened the permissions on the flash drive to improve security and the user cannot change them. As you raid this means that no files on the flash can have execute permission.
The options are now:
precede the script name with the command used to run the script (e.g. bash)
copy the script to somewhere where you can change the permissions and then do so (e.g. /usr/local/bin). This will, however, not survive a reboot unless you take the steps required to repeat this on every boot.
Run the script via the User Scripts plugin. This script could be the actions from the previous option with a script set to run on first array start.