Is Marketo <> SFDC sync for SFDC lookup fields not bi-directional?

Hi there,

I have a lookup field in the SFDC Lead object that does a lookup on the Campaign object. When I select a campaign in the field in SFDC, the respective Campaign ID is syncing over to the corresponding Marketo field correctly. But if/when I change the campaign ID value in the Marketo field, it does not seem to sync to the SFDC field. Ideally when I change the campaign ID in the Marketo field, the lookup value (i.e. the name of the campaign) would update in the SFDC field. Is the sync on SFDC lookup fields not bi-directional? 

Thx in advance

Colin

EDIT: Problem solved - there was a related flow in SFDC that was causing the Marketo > SFDC sync to fail in some circumstances..