A stock error is what happens when an order comes in for a product you don’t have stock of. For that to occur, the site where the order originated from would need to have a different stock level to the correct one. For your main site, this will never happen - since it is the single source of truth, and all orders coming in from other channels update your stock levels accordingly. For any of your other sales channels, this can occur when an order is made for an out of stock item, due to it being sold first on another channel.
So, more channels equals a higher risk of a stock error, since there are more locations for orders to occur.
The risk of a stock error is offset by having regular stock updates on your 3rd party channels. Shipatron has two levels of stock updating: Daily and Hourly, which is chosen based on the plan you are on.
Let's say you had two external sales channels, Channel One and Channel Two.
Channel One = daily update
Channel Two = hourly update
Channel One would carry a higher risk of a stock error, since it is updated less frequently.
Channel One = hourly update
Channel Two = hourly update
Both would both carry the same risk of a stock update, but is would be significantly lower due to the frequency of the stock updates.
Whether this ‘risk’ is a concern depends on how many orders are being made on those channels, and how much of a business concern it is for you to cancel an order after it has been made.