This is related to https://forums.macrumors.com/threads/ssd-not-booting.2043700/#post-24542408 I have an old 2012 MBP and have been running off an external HDD since last summer when the cable on my internal HDD melted in the hot Texas sun! Over the last several months, at random times I will be working on my computer and applications will start giving me the "Rainbow wheel of death". When I look at the light on my external encolusre, it is always solid green, meaning that nothing is being sent/received from my computer. I have to do a hard shutdown, and then things seem to be okay. In the past I just assumed that I bumped the USB cable enough to cause a hiccup in the data flow, and that somehow made OSX die on me. (I have never liked how USB ports were designed because they ALWAYS feel sloppy to me.) So this weekend I formatted and cloned my first ever EVO850 1TB SSD and go that working. Well, last night I was working on my laptop after work, and everythingw as okay, and right as I was finishing up some work before bed, I noticed I couldn't save anything. The green light on my external enclosure with SSD now in it was solid green, and yep, my old MBP was frozen again. WTF???? Clearly this can't be a bad HDD and SSD based on what I'm seeing. Do I have a bad external enclosure? Do I have a bad USB cable? Do I have a bad USB port in my aging MBP? Is there something wrong with the internals of my MBP? (I believe I literally melted my HDD cable this summer when I was running my laptop in 120 degree weather outside at the park...) Any ideas what is going on?