Annoying login behavior when unlocking windows

I have noticed something annoying and I have been unable to craft the proper search terms to get me useable results, so here goes.

When I log in or unlock my screensaver on Windows 10, WHILE I AM TYPING my username, the cursor jumps within the text box thus scrambling what I am typing. For example if I am user0001 and my password is Password1 If I press [ctrl]+[alt]+[del] and start typing what I end up with is either:

"r0001use" <=note, I type the username correctly, windows moves my cursor between the "e" and "r"
or more annoyingly something like "sword1Pas" in the password field.

I am using a standard desktop keyboard and mouse with no touchpad, (i7, SSD, 16gb ram). If I press [ctrl]+[alt]+[del] and count to 5 it does not happen. Its like windows 10 incorporates a delay, then reset the cursor function that has never been present before.

Using the exact same hardware with win7 or 8.1 works perfectly and it does not matter how fast I start typing my credentials. UAC prompts in win10 also seem unaffected. I don't mind the delay, but when it moves the cursor and thus scrambles the username or password, bad things happen.

Ok, let me try again, because apparently my question sounded like a hardware issue, and I can absolutely verify it is not. I am in a corporate IT shop and have access to dozens of pieces of identical hardware, and have troubleshot this down to a Windows Quirk/issue/feature.

I found another user (on a different site) that seems to have a similar problem but describes it differently:

With Windows 7 (and XP) I could walk up to a locked PC (without Ctrl-Alt-Del requirement) and start typing my password, even with the screen off, and the keypresses would all be sent to the password field, meaning that by the time the screen was on I was at the desktop.Same hardware, same scenario, but with Windows 10 it seems I have to press a key/mouse button, wait for a second or two before the password field is 'ready' before I can start to type the password.
This is annoying after many years of being able to unlock a PC in the same, quick way.

I just switched my PC to 1703 from 1607 (clean 1703 install) and now the issue is noticeably worse with no changes in hardware or any group policy or networking.