Explanation is in the note.
Try to reduce the precision.
SELECT CAST(cast(1.67574 as decimal(38,10)) / cast(10000 as decimal(38,10)) AS DECIMAL(38,10) ) conv_factor
returns 0.0001670000
SELECT CAST(cast(1.67574 as decimal(29,10)) / cast(10000 as decimal(29,10)) AS DECIMAL(29,10) ) conv_factor
returns 0.0001675740