@MultiTech_Visions @tsuji_koichi
I agree that I sometimes find inconsistencies in the behavior of Expressions. When this happens, I have to spend hours to narrow down the problem and then look for an alternative method to get the result I need. This is very frustrating.
I think that the AppSheet Expression interpreter code needs refactoring.
You have no idea… 
Yes, you are right about that. I also [ ]forget these signs. The expression interpreter does not see this error. But first I do the complex expressions I want to do in Excel. Then I make shorter alternatives to the expressions I wrote in Excel. I convert the expressions I get at the end into Appsheet expressions. In this way, I prepare my expressions faster.