2 points
Something to do with being unable to make the fuel tanks inert. If you Google it there’s quite a lot about it. I’m no expert so I can’t tell you what that really means
3 points
I did google it, that’s why I was confused; https://www.defensenews.com/air/2024/04/02/f-35a-lightning-cleared-to-fly-in-lightning-for-first-time-in-4-years/
It’s about lightning, not rain, and only affects the A variant which is, at least in the US’ case, a bit over half of all variants.
https://www.forbes.com/sites/erictegler/2022/11/23/air-force-f-35-lightning-iis-still-cant-fly-within-25-miles-of-lightning/?sh=7659da1e663e dated 2022, but covers the issue in detail.