Admin interface – use of "Please be patient"

In a recent update to one of our Admin interfaces (1 user), we added the following warning at the top, to remind the user that once they press the button, it can take several minutes to complete, and to avoid reloading the page and re-submitting, etc. (which has happened recently before the message was added)

The user, however, told us that they don't get the point of saying "Please be patient", especially in a Business/Admin interface, and asked if it's implying that the person operating is "Impatient". The user also mentioned that this message isn't "helpful", and is an incriminating statement.

I believe I've seen "Please be patient" written in other Software applications, and I thought this was a standard message to display when a process can take long / unpredictable time.

Was the use of "Please be patient" a bad idea here?
How would you formulate the message above?