A plugin conflict is something that occurs when two plugins are incompatible with one another.
For example, when you're having issues with one plugin functioning properly, often the problem is caused by a conflict with another plugin.
Note: Detecting the conflict is very important step to take because the problem can be resolved easily.
The following is known issue you may get when using Shield with other certain plugins.
Shield conflicts with Divi Page Builder Plugin
If you have Shield's Lockdown module enabled and you've used the option "Mask WordPress Version", it can happen that this option conflicts with Divi's Color Picker feature.
This sort of compatibility with that version masking option is to be expected. It can cause quite a bit of interference with plugins that rely on that setting to be accurate.