Strange behavior of a Colpitts Oscillator
The tank circuit values right now are such that it should produce
frequencies somewhere around 30 MHz

Not with the values shown - with the values shown (and a perfect BJT) it is more like 20 MHz.
The &quot;basic&quot; colpitts oscillator produces a frequency that is \$\dfrac{1}{2\pi\sqrt{LC}}\$ where C is the net combination of C1 and C2. This would mean that C = 50 pF hence the oscillation frequency will be 22.5 MHz.
The combination of C4, C6 and C8 will lower this frequency possibly sub 20 MHz.
Next is the BJT - it has a transition frequency of only 250 MHz and could easily add 2 or 3 ns delay to the emitter signal. This type of circuit is basically a phase shift oscillator - rarely does the oscillation frequency closely approach the peaking frequency defined by L2 and C1 (not C2). So, given that it is phase shift oscillator, the 2 or 3 ns added around the loop directly equates to a phase angle &quot;add-in&quot; of about 18 degrees and the oscillator will be forced to run significantly slower than 20 MHz.
A quick estimate is \$\dfrac{1}{1/250 + 1/20}\$ = about 18 MHz.
Throw in a few ten percent tolerances (capacitors and inductor) and the loading effect of the o-scope and you might be down at 12 MHz. Yes, the loading of the scope at the emitter does lower the operating frequency.
EDIT - the math to show what the resonant frequency is: -