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Multi-session Darks won't Load - v1.071 Windows 10
The loading process for each calibration frame asks which session and which filter to apply the frame to, so if it is over-riding this its another issue.
I don't know how it works behind the scenes but I would have hoped the logic would use the information provided and not try and make something up itself.
By all means use available information to check the user hasn't done anything daft but if the user says "use these flats for session 1 Blue filter" that is what I would expect it to do.