[Lennox 14HPX & CBX25UH] Dirty sock smell during every defrost cycle.

North Georgia, two story home, air-source heat pump, Lennox brand, indoor 14HPX, outdoor CBX25UH.

Been in our home for a little over three years now and one thing I've noticed regarding the heat pump is it produces an odor every defrost cycle like clockwork. I wasn't sure how to describe it but all my googling has lead me to conclude it's dirty sock syndrome. While it could be described as dirty socks, to me its more of a chemical smell; not terribly offending where it'll run you out of a room, but enough to catch you off guard if you walk under a supply vent.

Everything I've read says this is normal and only occurs during the first heat cycle of the cold season when the heat pump goes into heat mode and burns the debris on the coils. But this doesn't smell like burning dust, and it persists all throughout winter every time it does a defrost cycle guaranteed. Our temperatures mostly hover between 35 to 55 in winter with occasional drops to the 20s at night, so the unit defrosting doesn't really occur all that much. It really only goes into defrost at night where we don't notice it because we're all sleeping, but on cold, windy, rainy days it may defrost once or twice during the day and that's when it's most noticeable. The defrost cycle is very quick, lasting only 30 seconds or so before re-entering heat mode again so the smell is fleeting and brief.

Other than this, the unit seems to work perfectly fine. Nothing else to really complain about, just the odor that emanates during defrost. Does this really sound like dirty sock syndrome? I was reading ways to prevent or minimize this and some say to clean the indoor coils more frequently, clean the drain pan and flush out the drain line, place some copper or silver scraps in the drain pan to kill any microbes, install UV lights, etc. It hasn't really been a problem for us but I'm looking to get a little more info and maybe be proactive some come next winter I'll be more prepared for it.