Strange behavior with re-installed laptop

[MR ZenWiz]

My partner has a Dell Inspiron 3785 laptop as her main computer, with
Windows 10 and Xubuntu 18.04.4 installed on it.  (It came with Win 10
and I resized the C: partition so about 800Gb of the 1Tb disk is set
aside for Xubuntu.)

While I was in the hospital a couple of months ago, the laptop stopped
booting  Xubuntu properly.  When I finally got home to look at it, it
would come up in console mode only, no desktop manager at all, and it
never recognized the HDMI monitor we routinely use with it.

I wasn't sure what went wrong, so I decided to back up all her files
(using the Xubuntu DVD as the boot disk), wipe out the partition the
files were in, and reinstalled Xubuntu in two separate partitions -
one for the root / and one for /home.

This worked and the laptop now boots into Xubuntu by default, and the
Win 10 boot also still works.

However, many things are not working correctly.  We routinely use a
32" HD monitor with the laptop closed underneath a monitor stand for
the big monitor.

1. When I tell the system to reboot (from the GUI), the laptop does
not reboot at all.  I have to open the laptop, use the power switch to
shut it off and then again to reboot it.  This happens every time it
says it needs to reboot, like for a software update.

2. Without the power manager active, if I let the laptop sit for long
enough, the screen would shut off, requiring us to lift the laptop
screen long enough for it to realize it was supposed to switch on, and
then usually, but not always, the HDMI monitor reactivates.  (Yes, I
have it set to recognize all displays when they are plugged in.)

3.  I turned on the power manager and set it to blank the screen after
30 minutes (when plugged in) and shut off the screen after 60 minutes.
Once the screen shuts off, it does not come back when the mouse moves
or the keyboard is touched, we have to reopen the laptop to get the
screen back.

I don't think these are normal, but I'm not sure how to rectify this.

The only thing I'm not sure was quite correct is that when I
reinstalled Xubuntu, I told it to boot from the sda7 partition, which
is where Xubuntu is installed.  Since it can still boot either Xubuntu
or Windows, I presumed that this was correct.

Suggestions welcome.

Mark