So I had to replace the wheel cylinders on my truck because they were super rusty and gunky. I could tell these were going to leak in the next few thousand miles. Now when taking off the right side and putting back together it was smooth sailing. The left side was being a boar so I decided to cut the line and fit a new line up to the new cylinder since I couldn't get the fitting off at all. I put the new cylinder in after bending the line and everything seemed okay. Note I have the stock line on the other side. When I got back under my truck to continue working on my diff I noticed something odd. It was leaking out of the inlet fitting around the inside (against the line). I checked both sides and sure enough the stock line is leaking too in the same way. I know the line is right and it's not a stainless steel line. I tried re-flaring and putting it back down but same issue. It's not a large leak in fact it's barley noticeable I only noticed it because it shimmered but fluid is definitely coming out. What's weird is that where it connects to the splitter above the diff isn't leaking at all. Bad wheel cylinders? Bad lines? I don't know what's going on. I'll upload pictures here in an hour or so.

It's kind of hard to see here on my phone but there it is. This was after ~7 hours of being left alone and there's visible leaking and a droplet coming down the nut. Edit: also this is the stock line.