[KarlG]

@Becky

Thank you, borkify now working as expected.

@Kevin

Thank you for finding the cause of this.

I've entered 'export QT_ENABLE_REGEXP_JIT=0' in /usr/local/bin/sigil and it does indeed now run to completion without crashing.

Does take a bit longer, but it's not too bad. Took about 45 secs - 1 minute on my system (which is an older system with an Intel Core i5 CPU, so all in all that's not too bad)

At least we now know what the cause was - be interesting to see if Qt actually DO provide a fix for this.