Try ditching the spring pass. If you have trouble holding size without it try making two finish passes at .0035. I suspect you are roughing up the finish with the spring pass. The insert geometry is critical with that shallow cut. You may not be forming a proper chip. Seco makes a great chip breaker for light radial depths, I have used it for finishing 303 with excellent results. It is the FF1.
Are you running unsupported?