SQL Server 2014 Switch statement issues, violation of constraint or function - sql-server-2014

Question

I'm attempting to correct a partitioning mistake in SQL Server 2014. We have a data warehouse where all fact like tables are partitioned by year. When I originally setup the partition function I neglected to leave an empty partition at the end. These tables also have clustered columnstore indexes present (you apparently can't split non-empty partitions with columnstore, so I have to drop them as you'll see below).
I found SQLCat's managepartition tool, which has helped me create a temporary table for each table tied to the function. I then switch my last partition out to each temporary table, so that it is empty across all tables tied to the function and the split can take place instantaneously (as opposed to the 6 hours it took in testing on the dev box when I just dropped the columnstore indexes and did the split with the last partition not empty). The problem is that I'm having trouble switching the data back in.
ALTER TABLE SWITCH statement failed. Check constraints or partition function of source table 'DW_Dev.DDS.FactTable1TempSplit' allows values that are not allowed by check constraints or partition function on target table 'DW_Dev.DDS.FactTable1'.
Here's the thing, the SQLCat tool creates the constraint on each of the new temporary staging tables that should line up with the correct partition number. It looks correct, so I'm a little stumped. The partition function is based on a date key (column 1 (int)) and I've verified that only the year 2015 (the last partition, 3) is present in the temporary table.
select $PARTITION.pfYearlyGrain (20150101)
comes back with 3.
SELECT [Column1]
FROM [DW_Dev].[DDS].[FactTable1TempSplit]
WHERE [Column1] < 20150101
returns 0 records, same with >20151231 (just in case, if that existed we'd have other problems but I thought I'd check all the same).
I threw in a "is not null" as an addition on the constraint without resolving the issue.
The schema/function is as follows:
CREATE PARTITION SCHEME [psYearlyGrain] AS PARTITION [pfYearlyGrain]
TO ([SECONDARY], [SECONDARY], [SECONDARY], [SECONDARY], [SECONDARY])
GO
CREATE PARTITION FUNCTION [pfYearlyGrain](int) AS RANGE LEFT FOR
VALUES (20131231, 20141231, 20151231, 20161231)
GO
Complete code/commands below for one of the table combos:
Drop Index CI_FactTable1
ON DDS.FactTable1
GO
SET ANSI_NULLS ON
SET QUOTED_IDENTIFIER ON
CREATE TABLE [DDS].[FactTable1TempSplit](
[Column1] [int] NOT NULL,
[Column2] [int] NOT NULL,
[Column3] [smallint] NOT NULL,
[Column4] [smallint] NOT NULL,
[Column5] [smallint] NOT NULL,
[Column6] [smallint] NOT NULL,
[Column7] [smallint] NOT NULL,
[Column8] [smallint] NOT NULL,
[Column9] [int] NOT NULL
) ON [SECONDARY]
ALTER TABLE [DDS].[FactTable1TempSplit]
ADD CONSTRAINT [chk_FactTable1TempSplit_partition_3]
CHECK (([Column1]>20141231) AND [Column1] IS NOT NULL)
ALTER TABLE [DDS].[FactTableTempSplit]
CHECK CONSTRAINT [chk_FactTableTempSplit_partition_3]
ALTER TABLE [DDS].[FactTable1] SWITCH PARTITION 3
TO [DDS].[FactTable1TempSplit];
ALTER TABLE [DDS].[FactTable1TempSplit] SWITCH
TO [DDS].[FactTable1] PARTITION 3;
Also worth noting, the original fact table has no constraints, keys, indexes at this point. So the only thing I can think of is that for some reason the check constraint on the temporary table isn't valid/matching with the partition number/function, but I'm not seeing why. Any thoughts (other than that I really, really should have left an empty partition)?