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Nyssa - if you don't get any crashing when all plugins are ignored then:
My experience has been that removing a plug-in does not remove the plug-in customisation, so on reinstalling the PI everything is as it was. Which is consistent with uninstalling and reinstalling calibre.
What I do in situations like this is to remove all of them and then add them back alphabetically, don't bother trying to second guess most probable candidates, IMO its better to work methodically.
Using this approach I was able to narrow down the cause of calibre intermittently crashing, first time ever for me. it was a glitch in one of the PI's that had just had its kb shortcut process amended.
At the time I was testing the PI's after JimmXinu and davidfor had amended them.
Hmmm - that makes me wonder if one of them could be culprit in your case, IIRC the change was related to keyboard shortcuts on OS/X. I didn't test all the PI's they changed, only the ones I use.
BR