Hi Andy,
Thanks for the information you sent and my apologies for the delayed response. I tried generating your report on my end using the same AdWords API version and report definition as yours and was able to replicate the issue. However, I was also still able to generate the report by adding a filter as seen in my sample AWQL below :
String query = "SELECT Date, CampaignId, CampaignName, AdGroupId, AdGroupName, LocationType, MostSpecificCriteriaId, CityCriteriaId, MetroCriteriaId, "
+ "RegionCriteriaId, CountryCriteriaId, AdNetworkType2, Impressions, AveragePosition, Clicks, Device, "
+ "Conversions, ConversionValue, Cost, AllConversions, AllConversionValue, CrossDeviceConversions FROM GEO_PERFORMANCE_REPORT "
+ "WHERE AdNetworkType2 IN [SEARCH] "
+ "DURING 20170913, 20170913";
This being said, the reason for the error might be
due to the huge amount of data being downloaded, and as a workaround, you may further breakdown your report request as seen in my example. I hope this has been helpful.
Thanks and regards,
Peter
AdWords API Team