Other than Nick-o-Rama, I doubt Enter's subscriber loss is due to any controversies he's been in. As you pointed out, there was a pretty long lull in content in the beginning of the year and YouTube isn't particularly kind to people that decide to take breaks with their content.Comparing the drops to his videos releases, I came up with:
Late January: His later Nick-O-Ramas (Sanjay and Craig) and his Twitter deletion
Mid-June: Nothing, but this was during a lull of content and after his first two Corona videos
Late July: Shortly after "How the World Ended"
Mid-August: The Lion King review?
Now: Discord kerfuffle