J does not respell Fbb, Cbb, B## or E##
Pressing the default short cuts ( J and ctrl+J) does not change the spelling of Cbb, Fbb, B## or E##. These are enharmonic to Bb, Eb, C# and F# and pressing a shortcut should cycle through to these spellings. I'm not sure adding Cbb to a spelling for Bb for example is expected, but if this is necessary to fix the bug then I would do that.
To test this, enter these notes into a score and press either J or ctrl+j.
Workaround: press up arrow followed by down arrow to respell the pitches, then press J or ctrl+j if new spelling is still wrong.
A related bug is #290987: B# and Cb octave change . Once I get my development environment fixed I'd like to look at these two issues.