The DeBayer process writes PCL:CFASourceFilePath, which is later used by DrizzleIntegration to find the CFA file to perform a CFA drizzle.
PCL:CFASourceFilePath
owner Core
type String
attributes wr-pst-
value /Users/pane/NOT BACKED UP/2017-10-18 ic1396/JFP_9305_c.xisf
However, if the debayered images are run through SubframeSelector, writing the "accepted" images with weights keywords, the PCL properties are not preserved. As a result, DrizzleIntegration does not find the CFA file and drizzles the debayered version of the file (i.e., it is not performing a CFA drizzle).
It also drops other properties that would be useful to carry through, such as Instrument and Observation.