ALT + F3 shortcut key Doesn't Work Good

Hi… Sorry, I’m using google translate :
hello, is this the ALT + F3 problem to change the uppercase text, if I change one of the text in the line then the other text that I have changed will return to the lowercase … please help …
My system: ubuntu mate 18.04, Libreoffice Version 6.3.1.2.

tdf#119495