vtable errors are sometimes tricky to figure out. I would double check the following:
1. All methods in your classes are both defined in the headers (.h) and the source files (.cpp)
2. All methods have matching parameters
3. The number of methods are the same
4. If you have inherited classes, make sure that all virtual functions are implemented (this shouldn’t lead to vtable errors, but is worth checking)
5. Check that all used libraries are included and check that you are also linking their dependencies.
6. Try to compile your project with only a few test files, but link and use the libraries you need. A vtable error could mean that a library that is referenced is missing some of its dependencies or that these dependencies are not linked properly.
7. Start from the bottom and build up everything again piece by piece, if possible. This way you can try find the problem in your code.

If you can’t figure it out, see if you can create a simple example that reproduces the error and post it here. Maybe I or someone else that stumbles over this post knows what to do.

Good luck!

Nice of you for sharing your knowlage!
But your tips didn’t help in my case.
I get the error message “undefined reference to `vtable for …”
although the .h and .cpp files are synchronized and checked.
I’ve also cleaned the environment.
Have you any other tips?