Mojave - Disabled screensaver still comes on.

We have 5 mac minis all upgraded to Mojave and the screensavers are disabled on all of them. They are used for digital signs and never had the screensavers come on prior to the Mojave upgrade. We even added disable screensaver in all 4 hot corners. Still comes on.

Is there some way to permanently disable the screensaver on these Macs? We will NEVER want them to come on.