Sap is a natural product of pinewood and may be present in your flag. It can cause a slight blemish in the coloring. Neither stain nor sealers prevent the sap from seeping therefore it could come through in the future. Each flag has some level of charring which can cause the flag to slightly curl because the wood constricts when burned.
We carefully inspect each stripe and union before assembly and discard any piece presenting concern to prevent this from occurring, but we can't guarantee it.