Thx matthewb for your reply.
So are you suggesting that Magento can only run reliably against a single node MySQL DB? I have had it running for the last 5 years against a Percona XtraDB cluster and not had these cron issues I am reporting here.
I will try that setting you suggest, just in case it helps though so thanks for that suggestion.
Did you see my other post at:
where I ask about wsrep_convert_lock_to_trx - it would be really useful to get your view on that.
Thanks for your responses though, some ideas / insight into this issue is of course very welcome!