AgriChem
Have you been able to compare the readings of your manual rain gauge vs your WS5000 after a rain event? They should be located as close as possible.
Is your manual rain gauge a decent one, like a Stratus?
With the tipping bucket sensor on the ws5000 which I I believe is the Ecowitt wh40 , one thing to check, is if it sticks. There have been incidents where this occurs, it has happened to me. To test just press down on the bucket a few times and see how it bounces back, you may have to do it a bunch of times, and of course this will mess up you readings as you are doing it. If it does, you can spray some silicone around axel area of the bucket.
If you have already done or mentioned this , sorry for being redundant.
Edit: I see you haver had multiple rain gauges sent to you and they all behave the same. This is extremely unusual. I have 2 WH40s (One from Ambient and one from Ecowitt) and they work in agreement with my manual Stratus gauge, within 5% full scale