I have known about this for many years. However, I did Google the subject prior to posting and like many things there appear to be two sides to this story, also.
It may just be a "potential" for additional corrosion that doesn't actually materialize in real world experience.
I would venture that using plumbers flux as a cleaning process as you do may not create any issues.
However I would STRONGLY suggest never using an acid core solder for electrical work. Make sure you have a rosin core solder for electrical connections.
Larry
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