When running an aggregation with $group and $first and $last for "$$ROOT" I get this error:
2019-09-04T13:46:11.118-0400 E QUERY    [js] Error: command failed: {
	"operationTime" : Timestamp(1567619155, 1218),
	"ok" : 0,
	"errmsg" : "assertion src/mongo/db/pipeline/value.cpp:1368",
	"code" : 8,
	"codeName" : "UnknownError",
	"$clusterTime" : {
		"clusterTime" : Timestamp(1567619155, 1218),
		"signature" : {
			"hash" : BinData(0,"Ra+UKIAYLDFuDOJc2Q6v16BRwsI="),
			"keyId" : NumberLong("6694721349983666177")
		}
	}
} : aggregate failed :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:18:14
_assertCommandWorked@src/mongo/shell/assert.js:536:17
assert.commandWorked@src/mongo/shell/assert.js:620:16
DB.prototype._runAggregate@src/mongo/shell/db.js:260:9
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1062:12
@(shell):1:1
- is duplicated by
- 
                    SERVER-44945 aggregate failed at assertion src\\mongo\\db\\pipeline\\value.cpp:1365 -         
- Closed
 
-         
- is related to
- 
                    SERVER-44497 Aggregation: {"codeName" : "UnknownError"} -         
- Closed
 
-