Keyboard not working correctly in MATE

[Willyarma]

I have a Gemini PDA and it is working fine with LXQT.

I have installed MATE because I wanted the option of having both available and I found that some keys on the keyboard work and some do not.
On the keys that aren't working it appears that the FN key is being applied to them, so if I try to type r it actually tries to take a screenshot, and if I type n then it types nothing but (in a terminal window) the cursor flashes.

Please can anyone help?

[Willyarma]

I just tried removing MATE and re-installing it but only in part with:
sudo apt-get install mate-desktop-environment-core

After logging in, they keyboard all worked apart from r which is taking a screenshot.
I deleted that shortcut key using the Keyboard Shortcuts utility and then r started working again.

Then I installed more of MATE with:
sudo apt-get install mate-desktop-environment

After that, r was was still working, but now b and n don't work, these are the brightness keys, and they're not in the keyboard shortcuts list.

Any ideas?

[Willyarma]

Removing mate-power-manager-common fixed it