It's been freezing and requiring a reboot.
More recently, it boots to blank gray screen and needs about 3 restarts to boot.
Just added 2TB external, the first of which crashed repeatedly while transferring date from one external to another. Exchanged 2TB at store. New TB seems to work. Only crashed once during a transfer.
Not sure if addition of TB is the problem or not. Cannot remember if it was the same time or not, but very close.
Thanks for any help!