Incoherence between oscilloscope and spectrum analyser
Your oscilloscope shows an oscillation with a frequency in the \$\frac{1}{1\,\text{ns}}=1\,\text{GHz}\$ range. (So, yes, you're wrong, that's not a 1 MHz oscillation. I'm jealous of your oscilloscope, by the way.)

Your spectrum analyzer is set to cover 400 kHz to 15.14 MHz. You can't see a GHz oscillation in that range.