Did you change just one customer while leaving the entire rest of the list intact? Or did you delete all the customers you were not changing and only paste back the modified one? If you have not tried that, give it a try.
Also, I think I recall from other posts of yours that you use either the server or cloud edition. If so, @Joe91’s concern about the volume of data may be more relevant. With 1900 rows in the table, the quality and speed of your internet connection could be to blame. The largest batch update I’ve ever done was about 550 rows. That was the one I described above that gave me a problem. I can’t remember for certain, but as I think back, I may have resorted to truncating the pasted list or divided it into segments. And my internet connection is very high speed.