New answers tagged query-layer
I would check a few things: What is the Pooling limit on this map service? There are a lot of simultaneous query requests going out, and you may be hitting the max instance limit, which causes some server responses to act funny. You can increase the max limit, or maybe switch your isolation settings to Low Isolation. (I've had bad luck with low isolation ...
I've had similar issues in the past with setting a layer definition or visibility while it was still drawing. See this link: https://geonet.esri.com/thread/10158 Maybe that is your issue..
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