This test (and subsequent ones) in exhaust.js fail when the following are true: 

• featureFlagSbeFull is set to true OR it is a sharded environment
• This specific test is run prior
• numDocs is a certain value, observed with 2601, 3001, …

The test fails with uncaught exception: Error: [101] != [0] are not equal (or whatever the current findCommandBatchSize is != 0). 

Command to reproduce:

buildscripts/resmoke.py run jstests/core/exhaust.js --suites=core --mongodSetParameters='{featureFlagSbeFull: true}'

At first we suspected it was a plan cache issue but the test fails even with internalQueryDisablePlanCache: true. The failing test does in fact accumulate a first batch, but has the cursor result: (from adding logging for cmdResult here)

{    "cursor" : {
        "nextBatch" : [ ],
        "id" : NumberLong(0),
        "ns" : "test.exhaustColl"    },
    "ok" : 1 } 

After some investigation, the next direction that it might be fruitful to look into is the difference between PlanExecutorImpl::getNextBatch() (used by the classic engine) and PlanExecutor::getNextBatch() (used by SBE).