DIAGNOSIS Yeah, this one's common. It's usually coil whine from the fan motor's power electronics, or sometimes a harmonic resonance from the fan blades or the filter housing at certain RPMs.
FIX First, rule out a simple obstruction. Turn the unit off, open the front door, and check that nothing (like a cable or piece of paper) is touching the fan cage or is inside the intake area. Ensure the filter is seated perfectly flush. If it's clear, the noise is often a characteristic of that specific unit. Try running it on Auto or a lower manual speed (2 or 3)—if the noise disappears, you've found the problematic RPM range.
IF THAT DIDN'T WORK If the noise is present on all speeds and is truly loud/mechanical (more of a grinding), the fan bearing might be faulty. This isn't a user-serviceable part. You'd need to contact Molekule support for a warranty assessment or replacement.
HEADS UP Don't try to lubricate the fan motor yourself. The unit is sealed, and introducing any oil or lubricant can damage the electronics and will definitely void your warranty. Document the noise with a video to send to support.