Thanks for reporting this, it’s useful to know.
There are at least a few similar reports and for us it would be good to understand what could be the problem. In principle, when the Spectrogram viewer is not used (removed from the window via View->Viewer), our expectation would be that version 6.3 should behave similar to 6.2. The main difference then is that 6.3 has Java 17 included and 6.2 has Java 14 (with the exception of the macOS M1/aarch64 versions, they both have Java 17 included). Especially on Windows we have a slight suspicion that hard crashes there might be related to the Java version (see e.g. this thread).
In case you have any of those hs_err_pid nnn .log files on your system (not sure if on macOS they are in the same location as on Windows), we would be interested in receiving them.
-Han