I had a similar issue while learning Korean and watching Korean.
It started with the basic 네 (Ne), which is said countless times in interviews, and 90% of the times I hear it as "de", which i assumed was just an alternative way of saying yes, like a yeah/yes/yepp case

my Korean friends SWORE it's never said as "de", and even when I showed them videos where I constantly hear it as "de", they were like "umm wtf are you talking about, they're clearly saying
Ne"
It was a major mind**** for me