Mac Mini not displaying on older Dell Monitors

I have a Mac Mini (2012) and after the 10.10.5 update on the 25th it will no longer work with 2 older displays i have (single monitor setup). The displays are 2 Dell 2005fpw (1680x1050 @ 60hz native resolution), manufactured in 2006. The physical connection is made with the HDMI to DVI dongle. I've swapped cables & also tried on a 3rd and newer dell monitor using the same cable and input setup which worked fine. I've also applied the update to a second MAC mini with and tested with the same two monitors with the same result. My question is, are there any changes to the display driver with this release? Any other thoughts on steps to resolve this?

Troubleshooting steps:

PRAM Reset

SMC Reset

Physical Cable Switch

Dongle Switch

Tried VGA Input on monitors with a DVI-VGA adapter.\

Are these now just relics of an ancient time?