See this post for some ideas:
Specifically:
- Check for glitches / use the software glitch filter
- Confirm voltage level setting vs. I/O
(1.2V / 1.8V / 3.3+V on ‘Pro’ models)
… as well as:
- Check analog vs. digital view and confirm waveform/signal quality
- Check sample rate(s) are fast enough
(Target: 10+X the SCLK frequency) - Check ground connection(s)
(Suggest SCLK channel on SPI as it’s highest frequency signal)
Hope that helps!