You need to look for the plugin that is generating the issue. Follow these steps:
1. Remove the plugins one by one and check if the issue is fixed
2. Once you detect it is fixed, then open each of the .php files in the plugin directory and locate the text qa-app-users.php.
Note steps 1 and 2 can be simplified by just recursively searching for the text qa-app-users.php in the plugin directory
3. You will most likely find the text in a line that looks like this:
Then just replace the qa-app-users.php text with app/users.php so that the line becomes: