Hello Friedhelm,
nice to hear from you again.
Thank you for your reply which induced me to give an eye to settings (that are just the same as yours) and most of all to other PTC products.
I made a test with Modeling Express 6.0 and an edited axis remained unchanged after updating. General settings were the same, so I came into the properties of views behaving in different ways and compared them.
In the Mode form there's a frame whose english title should be Updating mode: well, as a first result it seems that a "Limited" 2D Associativity leads to my bad outcome! Setting it to "Full" will fix it.
At this moment I'm yet not sure that other view settings (mode Graphical/Classic, Face precision of graphic mode...) affect the behavior of axes, but now I know where to intervene to solve the issue.
Thank you very much for your prompt and regular reply.
Marco