Identifying the third party system modifications that may be responsible for the behavior you describe is a process of elimination, but if you don't know where to start EtreCheck can help with that:
Apple Support Communities contributor etresoft wrote a very useful app to quickly gather certain system information that may help point to a cause of this problem. Read about it here. It contains a link to download EtreCheck. Do not download it from anywhere else (such as may be found by following the results of an Internet search).
Run EtreCheck after starting your Mac normally (not in Safe Mode). It will take a moment to run as it collects its data.
Copy and paste its output in a reply. Use its "Copy report to clipboard" button.
Do not be concerned about anything that says "Problem" or “failed” or anything else that may appear in red. Those attention-getters don't necessarily indicate anything wrong.
EtreCheck was designed to remove any personal information (such as your computer's name and serial numbers) but if you see anything that looks like an email address or any other personal information that should not be divulged to others, please delete or obscure that information when you post the reply.
When you are finished with EtreCheck, quit the program. It occupies very little space, and you can keep it or drag it to the Trash as you wish.
