Scheduled Update and On demand data table

Hi all, 

I have a document with a data table A (in-memory) and 2 data tables B and C (in -memory - Import data setting + load on demand based on a join field with A). 

The update is running by 24h despite the analysis have to bring only A in-memory. What's happen?

The same analysis with all 3 data tables in-memory spent 6h to now I expected it to take less because it has to bring only A in-memory. 

If I try to open the analysis does not appear "Loading" progress but only a grey window without words. 

The version I'musing is 7.5.

Thank you