I have not seen the Config Editor for Synology. I will check that out, might save me some hassles.
I know that the Synology devices have about 5 php.ini files, the only thing I can think of is the one that needs the change, is not the one being changed? On my test setup with Xibo, I ended up changing the setting on all of the php.ini files via telnet. Some get reset after reboots, and some after upgrades.
Did you change the Configuration Editor so that it works on DSM 6? Also, I see people saying that the configuration is getting overwritten on reboot. So that might be something to note.