If you are loading the bipod forward it is pulling the stock away from the barrel which may be keeping it free floating and accurate.
When you are on the bags are you putting downward pressure on the rifle? If so this may be causing the stock to touch the barrel and causing your issue.
You can find touches during firing by removing the barrelled action and using candle black on the barrel and carefully refitting and firing it, then checking the barrel channel for any marks.
This may not be the issue but something to consider.
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