I don't do wine, so this suggestion may be bad for you... But I use vodka in the airlock for that exact reason. Water, over time, can harbour nasties that can infect a batch. Very little can live in vodka (the cheapo stuff) and if you get suckback then it only adds a tiny amount of ABV to your beverage.
As for the suckback, that DOES happen due to several reasons. The one more common for me is when I move the fermenter and the bucket/Better Bottle flexes.
The second most common reason is temp changes. Everything changes volume when it heats or cools, and the liquid you're fermenting is no exception. As the volumes increase they create suckback.
In either case, it doesn't spell disaster.