I did 3 things and seem to have better luck. not sure which out of the 3 are effective:
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Run MSFS2020 in administrator mode (find the .exe -> right click -> compatibility -> run in admin).
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Disable IPv6 (network adapter page, properties for your adapter -> uncheck ipv6. this has other effects not sure if it actually helps)
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Select CLEAR WEATHER PRESET in the world map BEFORE selecting departure airport. Load into the flight, then from the top toolbar change to live weather.