When deploying schema changes to a production instance the export to synapse link is not automatically updated and causes records to be omitted/not synched as expected. It would be useful if the schema changes for tables selected to be exported were automatically reflected in the DataLake storage container, or an option to update them was made available.
Below is a quote from MS Support that states the behaviour of not updating (and therefore not exporting all rows) is by design.
As we discussed that the issue is with Azure Synapse link, data not updating to the target table. Observed that one of the columns is added in the source and that not updated in the target one. I have verified this with our team internally and got an update that if we have any changes in the tables from the source form then we need to re link it to get update the columns in target. Currently this is a product behaviour.