This is a common misconception about the use of the BER Analyzer and Eye Diagram Analyzer for higher order modulator formats. Please search the forum for BER Test Set and you can find many similar topics.
Briefly, the BER Analyzer in the example is set to Measured mode, so it is not using the eye diagram it is only comparing the detected and transmitted sequences. The eye diagram looks strange and the BER does not change because it is not counting any errors. Probably because the sequence length is so short and the true BER is so small that there are no errors.
Also the eye diagram analyzer works well for RZ/NRZ OOK systems but it doesn’t correctly calculate the BER for higher modulation formats. IT is only there as a tool to visually inspect the eye diagram.
Regards