Sampling at two times the rate of the fundamental will suffice1, but your point is still well taken -- if the fundamental frequency of the system at resonance is, say 30Hz, and if the sampling rate of the sensor is, say, every second since a profile is not intended to be continuously constructed, but merely the point value sampled, then cyclic perturbations could be missed altogether, or aliased as noise/variance in the discrete samples, but the resonance signal would not be reconstructed.
I think the idea of resonance is interesting, but improbable. I think we will find a rare, but relatively mundane cause of dual fuel supply transitory obstruction.
1 "Nyquist (1928) pointed out that, if the function is substantially limited to the time interval T, 2BT values are sufficient to specify the function, basing his conclusions on a Fourier series representation of the function over the time interval T."