790 USFF, dual monitors boot issue

Hi everyone,

I have an Optiplex 790 USFF (i5-2400S, 8GB, 128GB SSD, Win10 Home). I can use dual monitors with it no problem, but booting up with both monitors plugged in will lead to LED 1, 3 & 4 led. Booting up with either Displayport or VGA plugged in alone, then plug in the second monitor is the only way to have dual displays work. Is this a known issue?

Thank you for reading.