I've uploaded a list of leads to Marketo. After the upload I initiated a smart campaign to fill in the missing data for all the relevant fields (like lead source, last product touched and etc). All of this data got populated on Marketo but for some reason not all of this data got synced to SFDC. I see that some of the leads (not all of them) have one field on SFDC empty, while on Marketo it has a value. I checked field mapping (it is a custom field), field type and validation rules. Everything seems to be ok. What can be the reason why this field is not always synced to SFDC?