Struggling with a mosaic of Rho. Colour is not consistant across the frames

[Tom OD]

Hi Pixinsight forum,
I started this project last year, and I have decided to try and add an extra hour per channel this year. The bottom right panel looks good lots of colour after Background Neut, DBE, and Colour calibration.
The bottom left panel looks washed out. There is 9hrs RGB in the word doc screen shot that I have attached. The RAW data in both panels fits look good, but the background values aren't quite the same, hence the bias I guess in the frames prior to BN in PI.
I use Background Neutralisation, then DBE, then Colour Calibration. Is there anything else I  can do to get the frames closer? My laptop is 32 bit and the memory cant handle the merge mosaic function.
Thanks Tom

[astropixel]

Have you tried ABE followed by ColorCalibration. I have found sometimes that ColorCalibration is not accurate when ABE is followed by BN. Does ABE also apply a bias to color?