Copy and paste doesn’t work properly from Linux client with PyCharm. It is possible to copy&paste but paste results in a NUL character trailing. This issue occurs when using the middle mouse button and it has been reproduced with NoMachine in NoMachine version 7.9.2 and previous ones. it can happen also with other applications.

As a possible workaround, paste text inside the session with ctrl+c or use the left button of mouse with option copy and paste.