The problem came back, but I fixed it again.
It was misreading of the impact. A lot of the time, the ball is coming faster, higher, and/or deeper than usual, and if i don't notice that, the racket edge ball is going to be happening.
Now, I focus a lot more on where the ball will be, and I can see these high/deep balls coming and make adjustments. Generally, I simply have to decide to strike the ball at a higher spot, or strike the ball at a spot a bit later in it's trajectory, or both. But it was mainly striking the ball at a higher spot. The second option is much better for fast serves though (looping later in its trajectory).
Simply deciding to strike the ball at a higher spot required a few changes. I wasn't really allowed to drop my hand anymore. I did that my thinking about forehand blocking, which is a stroke where you always keep your hand above the table. Doing so kept my arm bent, and also further in front of me, rather than unbent at the side of me. Then I had to learn to loop that way. My backhand had no issues because it already had these two things.
I can handle incoming loops much better today than 3 years ago, both with blocks and counterloops.
Thank you.