Since the latest sw release - the import function from .csv has become slower.
This is due to the fact that each newly created contact is checked on all Custom tabs to see if it does not belong to them.
This was done in favour of the speed of the Custom Tabs.
We sacrificed the loading speed of imported contacts for the speed of Custom Tabs.
When importing contacts please remain on the same page and wait patiently. (there is no other solution at present - this is intended behaviour by design.)
At the end of the import - you will receive a success message as usual.