We purchased like 40 of the Optiplex 5050 SFF in late 2017. It's been working well, but a few weeks ago, my users started getting boot up problems. On a cold boot (not sure if it only happens on cold boot), the startup process gets stuck with the Dell Logo on the monitor. This happens pretty often. I've looked at about 25 of these 40 5050 SFF we have and it happens on like 23 of them. I called Dell tech support when I thought it was only happening on one machine and rep told me they need to replace the whole motherboard. When I found out it's more than one machine, I declined this repair as there's no way it's a hardware issue.

Nothing was changed in BIOS. I looked at the "fast boot" setting and it's set to "thorough." There's a POST delay or something like that as well, and it makes no difference what this is set to.

Anyone have any ideas?