This behaviour breaks the name entry process and the "d" character has to be deleted first to be able to enter a name. If the cc/bcc fields are only selected with one mouse click then the problem does not appear on my PC but other users do experience this problem with just one click into these fields. They have reported me that they have started to see this problem since about 2-3 days.

This issue also does happen sometimes in the "to" field.

The attached video displays the problem on my PC which has been initiated with 2 clicks into these boxes. My colleague's PC shows the "D" in uppercase with just one click and one other colleague's PC doesn't have this problem at all.