Brand new AC unit makes whooshing sound and air “chokes”

My brand new AC recently started making a whooshing noise. It sounds kind of like a sudden gust of wind, but it repeats every few seconds. Another way I can think of to describe it: imagine a PC cooler running relatively silent, but still being able to hear it. Now imagine it increasing its RPM noticeably for just around a second. Now imagine it doing this continuously.

It's a ComfortStar split type 12k BTU.

It also doesn't result in air being blown faster but, when you can hear it, if you stand in front of the indoor unit, the air stops coming out for like half a second. Like the unit "chokes".

Things I've noticed and done:

• If I lift the front panel by 2-3 cm or more the phenomenon stops! I thought something might be pushing on the filters, or that it's not closing properly, but I can't see any issues…

• Efficiency doesn't seem to be affected, it still cools very well, but the sound is annoying.

• It only seems to happen on the low or auto fan setting. For example at medium, high or turbo setting seems to result in a steady stream of air uninterrupted by whooshings.

• It doesn't always happen. Sometimes I run it for hours with no annoying sound, other times it starts a few minutes after turning on the AC. Sometimes it stops for a while.

• I tried recording the sound but my phone doesn't really allow you to notice it when it occurs.

• I'm using the AC Unit with the front panel/lid just a bit open, is it wrong or bad for the unit to use it like that? (see picture with a red circle)