I think the issue is one of unwanted embellishments to simple chords, not some mysterious chord that biab doesn't recognize.

'Force simpler arrangement' or 'allow/disallow embellishments to chords' has a history of failing to override embellishments already assigned in the pattern editor to the style in use. That's been my experience anyway. You have to set embellishments to 0 for all instruments in the stylemaker to effectively get rid of them.

Regards

Alan