We have a strange issue at one of our customers:

One user cannot save any activity, activity stays in "new" status. When the user clicks "save" button, nothing happens, no error message is show "May not be blank", even the required fields (end time, customer) are empty. If the user logs into the system from another PC the problem remains. Other users which belong to the same acess group (checked both the Persons and Global users registers) can save the activities with no problems.
version 8.3 2017-07-16 (83250800) on ASP.


Any ideas?