Cursor won't stay put when working in Word Table

[luckyjsw]

I have just spent two very frustrating days trying to figure out why I am having problems editing my Word Table. This after surfing for several different "solutions" to my problem, with no success.

This is what happens:
2016 MS Word, inside a table.

When I try to click on a row, inside a box, or anywhere text in my document, for editing purposes, the cursor will not stick where I left-click OR right-click it. It jumps all over the pages, and will not stay where I am trying to edit.

I do not think it is my mouse, which works fine in all other documents, text programs.

Any advice much appreciated!