Has there been a problem with Network Manager (or other network stuff) in recent Linux distros ?

Especially Ubuntu-based ?

I have an old Dell 760 that had Lubuntu 15.04 (Vivid Vervet) installed on one partition, with Linux Lite and Manjaro on others. It sat around for about a year and a half before I could replace the PSU after it died. Naturally, as soon as I had the new PSU installed I tried to update the OS. Lubuntu wouldn't let me upgrade directly from VV to XX ! I tried installing 15.10 (Wily Werewolf) and ran into some strange issues. I could run apt-get, Firefox, and other appl'ns that relied on a network connection, but the Network Manager itself said I had *no* network connection ! I tried everything to start up a new network connection but nothing worked. I d/l'ed 16.10 (Yakety Yak) and installed that, and it got even worse. Now I couldn't connect at all, so I couldn't run apt-get or use the recovery mode to fix broken packages. But as long as I was running off the live DVD -- the same DVD I used for the installation -- the Network Manager functioned normally! Finally, I erased that one partition completely, and installed 16.04 (Xenial Xerus) LTS successfully. After a couple of hiccups on reboot, I had it running normally with full network access and ran the Software Update with no problems. (This is the short version -- I couldn't possibly remember all the details. I had another, working, computer and looked up tons of 'fixes' online, but all required being able to run apt-get on the afflicted computer.)

At this point, I might mention a complicating factor: this computer apparently has a dead ethernet port. I tried connecting a USB port to our cable modem and using a USB WiFi link. Both worked on boot from the live disk, but not from the installed OS. Evidently, a functioning ethernet port might have made things a bit easier.

In the process of doing all this, I got the impression that (1) Manjaro's version of GRUB dealt well enough with having other OS's and I'd just as soon leave it in place, and (2) Lubuntu's installation of GRUB may be what rendered the other partitions unbootable (though I don't really understand how). So I figured that having gotten Lubuntu up and working I would go ahead and reinstall Linux Lite (even I've hardly used it -- I'd like to look at it a little more), then Manjaro. Didn't get far with that plan before things went all pear-shaped. I reinstalled Linux Lite (i.e. on top of the old installation, without formatting the disk) and checked "download updates during installation". When finished, I got an error message that some applications weren't removed properly and I would have to reinstall them -- the same error message I got earlier from the Lubuntu installation. LL then had the same problems with the Network Manager -- "no connection" indicated, but I can use Firefox and Software Update. So now I'm thinking I need to do a fresh format-and-install for Linux Lite to work properly.

Is there some *known* bug etc. that would cause this ? Could I do an apt-get --reinstall on some particular package ? If so, what ?