P6 Pro Client vs Web - when you change dates

Good morning,

re: not started activities

Maybe this has been asked before. Please point me there is so.

In the client when I change the start date, the remaining duration stays the same and the finish date moves accordingly.

In Web PM when I change the start date, the remaining duration changes and the finish date does not change. There is an exception

Web examples:

S 9/10/18 F 9/14/18 - RD=5

change S to 9/11/18 - no other change seen on screen. Click save. Result is S 9/11/18 F 9/15/18 and RD is now 4

change S to 9/17/18 - no other change seen on screen. Click save. Result is S 9/17/18 F 9/17/18 and RD is now 0