This has been a LONG term issue for me and unfortunately I have been remiss in reporting it. First I have a 64g iPad Air 2. I am a prolific highlighter and MANY time I would highlight something only to have it disappear shortly (a second or two) after. Other times I would highlight and it does not apply or show until what is a significant delay. This behavior negatively impacts productivit! I may be doing something wrong or perhaps a setting is wrong. Forgive me for the delay in reporting!
Bob