Labels are wrong - language items shown instead

I have just installed JEM 2.2 on a Joomla 3 website. Most of the labels on the interface are displayed wrongly. For example, on the side menu bar:
Instead of 'Venues', COM_JEM_VENUES is shown
Instead of 'Settings', COM_JEM_SETTINGS_TITLE is shown
etc, etc, please see screenshot 1, JEM Control Panel.
The same thing has happened in all the other JEM screens. Please see screenshot 2, JEM Events page.
Could you please advise how I can fix this please?
Thanks

Hi, it seems that your language files are somehow corrupted. Did you change something in the language files (and forgot something like a comma etc.)
Perhaps it helps to reinstall.

I appreciate your reply Jojo, thanks for your suggestions.

I did not make any changes to the language files after the installation. I tried uninstalling and then reinstalling JEM and that did not fix the problem. I also tried copying the JEM language files from one of my websites where it is working in case they were corrupted, and that did not work either.

How can I find the source of the problem? Is there something else I can try to fix this?

It don't know why, but it is possible that old JEM language files are in the joomla language folders and block then the language files inside of the JEM language folders. Please have a look for that! If JEM language files are in the joomla language folder, you must deactivate or delete them. Only like this the new language files inside the JEM language folder can work!

Thanks, you put me onto the 'right track', and I have now solved the problem!
The field labels were only wrong in the back end (administrator), they were OK in the front end. I looked at the various JEM language files under the administrator directory and found that one of them had a 2015 date. It was in the following directory:
site name/administrator/language/en-GB. The file was called 'en-GB.com_jem.ini'.
I removed that file and all the field labels returned to normal.
This was a new installation of JEM, not an upgrade, so could there be something wrong with the 2.2 installation package?

Good to hear that you solved the problem.
Did you ever had earlier an old JEM installed you uninstalled after? Because, some uninstallation did not delete language files in the Joomla language folders.