I have the same issue as Bug ID 140522.  Using Windows 10 20H2; Intel Core i3 CPU, 540 @ 3.07 GHz; 8 GB RAM; 240 SSD; Utilizing and older PS/2 Gateway 2000 keyboard.  The keypad was working fine until a couple of months ago.  The keypad works fine in Calc and Presentation; happens only in Writer.  I had to install Apache OpenOffice and Textmaker to keep issue from having.  I can use the numbers over the qwerty letters, but it takes much longer and more prone to typographical mistake.  I did try to turn the NumLock key off and on several times; rebooted multiple times while turning off power completely at surge protector for 2 minutes.  I did not get into the Bios, as my internet search seemed to not be Bios related.  I looked for other PS/2 keyboard drivers, but was not able to find a suitable one; Windows 10 said the best driver was already installed.  I didn't want to push my luck with a different keyboard driver.

I checked my wife's pc with Windows 10 and a less than one year old hardware setup; I found the same issue; multiple numbers when you press one number on the right had keypad.

I found this same issue using LO 7.1.  I uninstalled 7.0.5; uninstalled 7.1; reinstalled 7.0.4 and found the same issue with multiple pages of one number when you press the keypad.

Along with LO freezing up on a regular basis, I will have to utilize Apache OpenOffice and Textmaker for my spreadsheet and word processing needs.

The PS/2 keyboard keypad works just fine with all my other programs; I even checked Notepad and no problem.  Keypad works fine with Wordperfect on my wife's pc.  Keypad works fine on all of my browsers:  Seamonkey, Palemoon, Firefox, and Brave; works fine with email.  Works fine with LO Calc but not LO Writer.  I use the keypad a lot in my daily work and personal usage, with my Accounting practice.  So for me this is critical.

All I could think of is with the upgrade to Windows 10 20H2, my old PS/2 keyboard (which works really great), LO Writer is reading the keypad as a repeater; must be some setting within LO that does not like the PS/2 keyboard.  I don't remember this issue with my prior usb generic keyboard (about 6 months ago). 

I hope this helps.  Thank you for your kind and prompt assistance.