During working on my project I got the following warning from Webpack:

WARNING: There is another module with an equal name when case is ignored.

After some googling I got a solution! Check all the 'require' keywords used in your project for casing. Well that did not work because all the casings where the same. And then... Suddenly I found the issue. Check both console windows below. The windows above gave the warning. The other window does not give the warning.

Did you see the problem? Well... It is the casing of the drive. The first windows has a lower case c: and the last one has a uppercase C:.

This problem occurred because I opened the first windows from Total Commander and the last window from the Start Menu.