I'm sure many here have had to deal with Bees in the pitot tubes or static port during the summer. Did you know they will cause pressurization issues also? I received a call the other day on a Citation 550 with a pressurization issue, and the pilot noticed the boots looked partially inflated. I told him to clean out the overboard exhaust tubes for the vacuum ejectors. The exhaust tubes for the vacuum ejectors are visible on the belly just aft of the aft pressure bulkhead. Kneel down by the baggage door and look slightly forward on the belly and you will see them. When dirt daubers build nest in one or both tubes then the vacuum ejectors cannot create the vacuum required for the pressurization control and to keep the boots pulled down tight. The issue can be easily verified. With the engines running have someone put a hand a few inches from the exhaust tubes, if they do not feel air coming out then the exhaust tube needs to be cleared.

Thanks for the tip! I always keep my pitot tubes covered but not my static or other drain vents. If I end up with any funny behavior I will definitely check these!

Over pressurization happened to a G-IV because of mud daubers.

https://asn.flightsafety.org/asndb/320315