There are always challenges when moving from something familiar to something similar but different. When you've been working with that "something familiar" for a very long time, some things become second nature. But when you move to "something similar but different", sooner or later you hit an error and become convinced it's not working like it used to.
This is a companion discussion topic for the original entry at https://paulswithers.github.io/blog/2024/12/12/forall/