I have same problem as Using CTRL +V in Mail app on Mac Os X but in Mojave and for more apps.
I have Ctrl+v setup as paste in System Preferences -> Keyboard -> Shortcuts. This works fine in many apps but in the mail and safari apps it does a page down. If I hit Ctrl+v at the bottom of the text window then it works as a paste, meaning I can paste stuff into a text box but only at the bottom. How can I stop it doing this page down?
The solutions in the other questions involved mapping the command key to the Ctrl key using a feature that I can't see in Mojave. In any case this is not acceptable as I want to be able to use the command key in other situations.