insert into select performance slow on 1.4 release

We have a 1.4.2 Columnstore instance running with 1 UM and 4 PM separate nodes. We have a routine process that runs an 'insert into .. select' statement with a larger query.. results are about 3.2 million rows to insert. This is being run on our 1.2.5 instance, and can complete in around 1 minute. WHen running this on our 1.4.2 instance, it does not seem to ever complete when letting it run. The select portion will complete on it's own in about a minute as expected, however the insert into seems to be taking a very long time.. in fact I have yet to see it actually finish.