Turns out I had the Variable in my formula and you need to "Record (Single) Variable" in. It worked on my other flow because the API of the variable on the one iwth the issue was the same as the "Record (Single) Variable" on the other flow.
ベストサンサーを見ても解決策は全く理解できませんね。
So my issues is solved, some refresh/caching problem going on there I think since field which was not available before is available now thanks to Trevor and Mikey for their input!
キャッシュの問題とか言っているけど...