ability to highlight is intermittent and on highlighting it sometimes spontaneously closes

I have Adobe Digital Editions version 4.5.12.112 running on Windows 11 Enterprise v 22H2.

More often than not the highlight function is greyed out, although occasionally it isn't - restarting ADE or the PC does not make a difference to the frequency of the problem.

When highlight does work, sometimes after highlighting the selected text ADE spontaneously closes, and on reopening the highlight is not there.

Is there anything I can do to resolve either of these issues?