I am working with an Org, and I have used the LeadOrContactID standard field on Campaign Member as a convinient lookup to a campaign member without having to have a decision element to determine which type of ID is being used, and to do a seperate lookup.

I have this on one flow that is around 10 months old, and has been working perfectly.  I needed another flow on Campaign Member yesterday, so I used it again.  I completely tested and it was working fine as of yesterday end of day.

At about 10:30 this morning, I began getting users emailing about errors with records that involved both of these flows that could not save because of an error.  When digging in to it, I found that the Lookup portions of the flow were failing, becasue the flow could not find a Campaign Member record when using the LeadOrContactID as one of the criteria.

So I figured I would create a custom LeadOrContactId field, using a formula field. I verified on the page layout that the field is returning the correct lead or contact ID.  But the flow still fails, for the same reason - It looks like it cannot be used as the criteria for lookup.

I re-crafted both flows with decision elements to take care of this.

Any idea why both flows would quit so suddenly?