Thanks for that. Have now updated Word, and set up regular updates.
Prior to the upgrade I definitely could scroll up/down a line at a time in Word, using single-headed arrows in the bottom right corner. I have also seen versions with both single-headed (line by line) and double-headed (page by page) arrows. But after the upgrade it's a double-headed arrow, and I can't scroll line by line. Like you, I don't understand why or how it should have changed.
This is particularly irritating because I can't get the mouse to scroll by finger stroke in Word either, though it works on web pages. But perhaps that's standard.