This is a yeast infection. Small amounts can be produced by all yeast, but commercial yeasts have this sort of thing minimized.
If this is happening repeatedly consider wine and winery sanitation. As the chaps before have said keep everything topped up and correctly sulphited. If you brew in a particular area, make it yeast unfriendly- cleaning surfaces and stuff with strong sulphite solution. If you think it might be caused by particular equipment thoroughly sanitize, and consider leaving all vessels with a slug of sulphite solution in them. This method 'always clean' is better than 'wash before use'. Finally ... just to really set your head on fire - older equipment can have scratches/marks/nooks and crannies which harbor grobblies - you may want to consider replacement.
Gluten free, caffeine free, dairy free, fat free – you gotta love this red wine diet!