We are seeing sporadic "Internal Salesforce.com Error" for SOQL using an external object. When it works SOQL returns value and I am able to see the results. I am not able to put finger on what is causing this internal error and what it means. Any insight to debug the issue would be really helpful. 

Following is snippet of Debug log - 

6:37:16.0 (15971342)|SOQL_EXECUTE_BEGIN|[42]|Aggregations:0|SELECT Id, start_at__c, end_at__c, Id__c, name__c, canvasId__c FROM courses__x WHERE (canvasId__c = :tmpVar1 AND start_at__c <= TODAY AND end_at__c >= TODAY) ORDER BY end_at__c ASC NULLS FIRST
16:37:16.0 (982620934)|FATAL_ERROR|Internal Salesforce.com Error
16:37:16.0 (982666130)|CODE_UNIT_FINISHED|CBS_CourseController.getCoursesForCurrentUser
16:37:16.0 (987728779)|CODE_UNIT_FINISHED|Aura

We are seeing sporadic "Internal Salesforce.com Error" for SOQL using an external object. When it works SOQL returns value and I am able to see the results. I am not able to put finger on what is causing this internal error and what it means. Any insight to debug the issue would be really helpful. 

Following is snippet of Debug log - 

6:37:16.0 (15971342)|SOQL_EXECUTE_BEGIN|[42]|Aggregations:0|SELECT Id, start_at__c, end_at__c, Id__c, name__c, canvasId__c FROM courses__x WHERE (canvasId__c = :tmpVar1 AND start_at__c <= TODAY AND end_at__c >= TODAY) ORDER BY end_at__c ASC NULLS FIRST
16:37:16.0 (982620934)|FATAL_ERROR|Internal Salesforce.com Error
16:37:16.0 (982666130)|CODE_UNIT_FINISHED|CBS_CourseController.getCoursesForCurrentUser
16:37:16.0 (987728779)|CODE_UNIT_FINISHED|Aura