Conversion failed when converting the nvarchar value '0.000000' to data type int
In your code I see a CONVERT(NUMERIC,...) but not a CONVERT(INT,...).  So where is the converting to data type int happening?

SELECT CONVERT(INT, N'0.0000')    -- Conversion failed message
SELECT CONVERT(NUMERIC, N'0.0000')-- Converts to 0 


For what it is worth, if you do the following, you also get a '0'.

SELECT CONVERT(INT, CONVERT(NUMERIC, N'0.0000'))


It seems that FLEXFIELD4 is NVARCHAR. If there is some other conversion involved that your code does not show, then that might clarify the issue.