Wanted to get some clarity surrounding contacts that have been sent material, have had their engagement picked up but also been recorded as "email bounced".
How are contacts being scored/recorded for engagement but also recorded as being "email bounced"??
The scoring campaigns might have triggers that do not account for the fact that the email bounced. Hard to say without seeing the scoring campaigns. I suggest you go into the Activity Log of a lead and see what happened - look at when the scoring fired, what is the scoring campaign and see if there is a fault in the scoring logic. Or you could set up a campaign to reset the score of a record if the email bounces.
There are two things going on here:
Marketo doesn't do much other than temp block the lead who bounces or possibly invalidates them. You should explore setting up list cleaning automation system.