Beer was known to go bad on long voyages. So long as the beer held out though there was no scurvy.
Beer staying fresh seems like a proxy for voyage duration. Longer trips means more likely to have run out of beer/vitamin C sources. No beer probably means no dock where sailors could have consumed anything other than highly preserved food.
Beer does not cure scurvy. Scurvy is caused by a lack of vitamin C, which is not in beer.