In some cases individual or folder syncs will not carry over new content in a synchronization, but updates to old content does sync.

This can arise when there is too large a discrepancy between individual content/folder sync knowledge and full sync(the sync used in workarea>settings>synchronization>profiles) knowledge. Sync knowledge is the record of previous syncs and the two types of syncs knowledge need to match otherwise you can start to see issues with new content syncing over.

Do a full database sync which will bring the full sync knowledge in line with individual content/folder syncs.