Server Version#: 1.19.3.2793-36efde971
.plexignore file isn’t read until after directories. This causes Plex Server to scan files and folders that may be ignored, bogging down the scan if an ignored folder has many files.
A work-around is to create/move the .plexignore file to the end of the bottom of the directory structure that comes first. I.e. The first sub-directory within the first sub-directory within the first sub-directory… rather than the root folder.