Thank you very much for the additional information.
I have been able to reproduce the described behavior, but
- only on Windows,
- only with keyboard layout "English (USA, International) QWERTY", and
- only for yEd's inline label editor.
Due to the last point, there is a fairly simple workaround: Instead of editing label texts with yEd's inline label editor (that is opened with F2 or from the context menu "Edit Label" action), use the "Text" editor field in the properties view in yEd's lower right corner. (If you click into the corresponding text field close to its right border, a larger text editor dialog is opened for more comfortable text editing.) Aside from that, you could also use the "Text" editor field in the properties dialog that is opened with F6, or edit label texts in the structure view in yEd's lower left corner.
That said, this is a strange problem indeed. After a first code review, I could not find differences in the inline editor code compared to the other editor codes that would explain the differences in behavior. To be honest, at this point I am not even sure if I will be able to identify the root cause, because the cause might very well lie in an operating system specific part of the Java runtime library or one of the closed source third-party libraries we use in yEd. (In other words, do not wait for this to get fixed but use one of the workarounds mentioned above.)