Op Amp adds spectral components to amplified output signal
Although the Schematic is just a logical diagram , if the loops were as big as the high impedance paths suggest, it becomes a big loop antenna to E Fields created by power line cables. Considering the possible ground sources from Sig Gen and Scope, there is ample opportunity for large CM noise effects on intermodulation or basically distorted amplification.  Considering the attenuation of 50Hz thru your high pass filter is -12dB @ 50Hz, it is still bigger than your signal. Make sure a supply cap is near IC.

So many times I have been telling folks to use short inter-connections on high impedances, caps on supplies and minimize single wire loops, otherwise use twisted pair. It's lack of willingness on users to research proper breadboard skills and measurement methods.

Start with clean ground signals, then clean supply , then check each side of each component for noise and make the breadboard look it should and show before and after photos of your construction and results.