refresh error DM_GWPipeline_Client_AsyncOperationStreamingRetriesExhausted

{"error":{"code":"DM_GWPipeline_Client_AsyncOperationStreamingRetriesExhausted","pbi.error":{"code":"DM_GWPipeline_Client_AsyncOperationStreamingRetriesExhausted","parameters":{},"details":[],"exceptionCulprit":1}}} Table: External_Sales_Bridge.

I read some other threads and the only proposed solution was either restart the gateway or upgrade the gateway. What's the technical explanation of this error? Is there only a limited number of refreshes that the gateway can handle simultaneously? or does it mean something else?