Why Apache Flink SQL validator is giving NPE for this CEP SQL?

Question

Here is my Flink CEP MATCH_RECOGNIZE sql.

SELECT E.* 
FROM MyEvents 
MATCH_RECOGNIZE ( 
ORDER BY procTime 
MEASURES
    A.id as id,
    A.name as name
AFTER MATCH SKIP TO NEXT ROW 
PATTERN (A) 
DEFINE 
 A AS source='XYZ' and name IN ('EVENT_SRC1', 'EVENT_SRC2') 
 AND EXISTS (select eap.* from MyEvents AS eap where eap.name IN ('EVENT_SRC1')) 
 AND EXISTS (select eam.* from MyEvents AS eam where eam.name IN ('EVENT_SRC2')) 
) AS E;

Gives error as

Caused by: java.lang.NullPointerException: null
    at java.util.ArrayDeque.addFirst(ArrayDeque.java:228)
    at java.util.ArrayDeque.push(ArrayDeque.java:503)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:49)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:33)
    at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:139)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:134)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:101)
    at org.apache.calcite.sql.SqlOperator.acceptCall(SqlOperator.java:884)
    at org.apache.calcite.sql.validate.SqlValidatorImpl$Expander.visitScoped(SqlValidatorImpl.java:6009)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:50)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:33)
    at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:139)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:134)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:101)
    at org.apache.calcite.sql.SqlOperator.acceptCall(SqlOperator.java:884)
    at org.apache.calcite.sql.validate.SqlValidatorImpl$Expander.visitScoped(SqlValidatorImpl.java:6009)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:50)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:33)
    at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:139)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:134)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:101)
    at org.apache.calcite.sql.SqlOperator.acceptCall(SqlOperator.java:884)
    at org.apache.calcite.sql.validate.SqlValidatorImpl$Expander.visitScoped(SqlValidatorImpl.java:6009)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:50)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:33)
    at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:139)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:134)
    at org.apache.calcite.sql.util.SqlShuttle$CallCopyingArgHandler.visitChild(SqlShuttle.java:101)
    at org.apache.calcite.sql.SqlAsOperator.acceptCall(SqlAsOperator.java:121)
    at org.apache.calcite.sql.validate.SqlValidatorImpl$Expander.visitScoped(SqlValidatorImpl.java:6009)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:50)
    at org.apache.calcite.sql.validate.SqlScopedShuttle.visit(SqlScopedShuttle.java:33)
    at org.apache.calcite.sql.SqlCall.accept(SqlCall.java:139)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.expand(SqlValidatorImpl.java:5583)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateDefinitions(SqlValidatorImpl.java:5408)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateMatchRecognize(SqlValidatorImpl.java:5287)
    at org.apache.calcite.sql.validate.MatchRecognizeNamespace.validateImpl(MatchRecognizeNamespace.java:38)
    at org.apache.calcite.sql.validate.AbstractNamespace.validate(AbstractNamespace.java:84)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateNamespace(SqlValidatorImpl.java:1110)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateQuery(SqlValidatorImpl.java:1084)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateFrom(SqlValidatorImpl.java:3256)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateFrom(SqlValidatorImpl.java:3238)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateSelect(SqlValidatorImpl.java:3510)
    at org.apache.calcite.sql.validate.SelectNamespace.validateImpl(SelectNamespace.java:60)
    at org.apache.calcite.sql.validate.AbstractNamespace.validate(AbstractNamespace.java:84)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateNamespace(SqlValidatorImpl.java:1110)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateQuery(SqlValidatorImpl.java:1084)
    at org.apache.calcite.sql.SqlSelect.validate(SqlSelect.java:232)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validateScopedExpression(SqlValidatorImpl.java:1059)
    at org.apache.calcite.sql.validate.SqlValidatorImpl.validate(SqlValidatorImpl.java:766)
    at org.apache.flink.table.planner.calcite.FlinkPlannerImpl.org$apache$flink$table$planner$calcite$FlinkPlannerImpl$$validate(FlinkPlannerImpl.scala:141)
    ... 20 common frames omitted

Whereas, If I remove 2 EXISTS conditions then it works. Also, I tried creating another table for my datastream and used that in inner query instead, but still getting same error? Anything an I doing incorrect or such syntax is not supported in Flink CEP SQL?

Note- I am using 1.11 version. I have tried EXISTS clause in normal FLINK SQL (i.e. select ....from....where..) and it works. But not with Flink CEP SQL. Thanks.