Does it not seem odd that it's only the anemometer being affected when I am in the room? And that it has only just started happening? The only thing I can think of, is that the recent update has done something.
Agree the behavior is really odd. Why are you impacting the readings? Why just the one sensor? Very strange! Not sure how software would be impacted by you being present or not. Definitely sounds like a signal problem. The software change might have reset some threshold value in the program, but likely the underlying problem was there before.
While I am not an electrical engineer, I have worked with communication radio installs on vehicles and in the field as well as wifi setups in homes and offices. The shadow effects others have suggested is the usual suspect. I have seen people's body's directionally impact 2m signals, for example. Ditto on building structures and even glass. I am assuming each of the sensors are in different directions from the console. Might want to key in on what is directly between the anemometer and the console. Building materials? Wiring?
Do you have any medical devices implanted? Pins, pacemaker, joint replacements, etc.? Wireless hearing aids? VERY long shot on those items but possible sources of interference. Do you wear a smart watch of some sort? I have seen faulty phones impact signals.
I DO have a long history with electronic manufacturing, especially Asian outsourcing. (Twenty plus years in Silicon Valley, including stints at Palm, 3Com, Cisco.) One of the trade-offs when going with lower cost units like these Ecowitt's is that design, component quality, and assembly, to some degree, has to be less. "You get what you pay for." The units could be picking up problems that your Davis setup would just shrug off. That is NOT to say these are shoddy units. It is a cost trade-off. Just like buying a Chevy versus a BMW (or whatever the UK version of that analogy is!).
One other suggestion. It is not a high sensitivity solution, but Netgear makes a phone app called WiFi Analytics. It has proven helpful to me in finding dead spots. It has a record function and allows you to save and track different locations. You could set the phone out in various locations around the sensor and around the console. I am thinking of an arc around each, with maybe three or four placements. Place the phone, record for a while, walk into the room and hang out. See what changes. See if it gives you any insights of what is messing with the signal.
Hopefully Lucy and the team will get this resolved for you. They have been amazingly responsive. Best of luck on resolving this!