From the facts presented it seems probable that this particular LP-S got out of the factory with an out-of-spec suspension (or it's old and worn out). It's behaving like a cartridge with a more compliant suspension than a typical LP-S.
Suggestion: try it on a different tonearm and see if it exhibits unusually low resonance frequencies there too. If so, the cartridge suspension is suspect.
P. S. Also, try reducing VTF. Excessive VTF could contribute to such behavior. And don't quote me what your scale or the manufacturer's guidelines say, just try it. :)