Strange blue border around Selected window/link

THX, I tried that just now, after updating the OS, and both of the reps I talked to earlier had me try it, before updating - I'm a little surprised neither of them had heard of this issue - I know someone has, and knows how to change it back

THX - If you're referring to my post about 'trying to get back to Apple' - it was just that, trying to update Support about this since neither of the 2 reps I talked to knew about the issue when I called

I got an email from Support about it and the included link was a dead end - I was just hoping to educate them ... like I did RE a call a few weeks ago about an older MBPro with a trackpad issue. Turned out it was some kind of short 'fixed' if I touched the case/bezel with one hand and used the other on the trackpad - problem solved. The Rep I talked to at that time and I had discussed this possibility and ruled it out assuming it was more a system/OS issue than a mechanical one

RE the '[Personal Information Edited by Moderator]' thing apparently they chose to remove the Case # is all

Problem persists - and I Reset to Defaults in the Keyboard > Shortcuts window; and except for the Reset, the first Rep had me do the Safe mode startup and Disable/Enable thing

THX and I have faith we can figure this out - also here's a screenshot where I noticed the blue border overlaps the Doc - maybe a small clue ?

I didn't try this because something I did in the previous recommendations the problem appears to have been fixed - last thing I did was the - Uncheck "Enable Full Keyboard Access" in System Preferences > Accessibility > Keyboard > Navigation

I still say I must have accidentally hit the keyboard shortcut that toggles that particular Pref because I don't believe I've ever been in these 'Accessibility' prefs windows

I did NOT 'install and run any "cleaning", "optimizing", "speed-up...." at all on this device

Per MrHoffman's suggestion - should I still run and post Etrecheck ?

THX to ALL

Short follow-up -- In Mail now I have 5 emails RE this and when I click on one it has the usual dark blue 'selected' background AND the other 4 have a light blue background

I don't have any others like this that share a 'thread' but I like it and can live with it - no other apps I've checked seem to have any issues like this

THX - "Organize by Conversation" is currently un-checked and as long as apps are working like I'm used to I'm going to leave it. I don't have many "Conversations" so just hadn't noticed that feature before