Attribute over aggregate function shows an internal error

Summary

In simple cases when an attribute function is used over another aggregate function, it works fine. But when the same aggregate is put inside a case when statement, the calculation shows a syntax error

Content

Hello, 

I am working on a dataset as follows :  

When I use aggregate function inside an attribute function, it works fine. but when the aggregate is put inside a case when statement as follows, or even the aggregate is multiplied, added, subtracted or divided by a number, a syntax error is shown, though the functional output is the same :

 

Another issue is that while creating a calculation in data visualization, when I use nested attribute functions, (an attribute over another attribute function) the calculation works fine. But when I apply it to the visualization, it shows a general error.