For me my mind will drift off and I won’t be able to stay focussed on completing repetitive tasks.
As a result thoughts of failure, stress, frustration, distraction etc will kick in and I will actively start avoiding it and sabotaging completing it until the last minute.
It only makes sense for me to try and avoid that scenario so I would say yes I have a fear of repetitive boring work/tasks but I don’t think its a phobia in the strict sense.
It varies quite a bit. People management, creating documentation, architecture, coding, problem solving etc. I make pretty broad jumps so it helps with resetting my focus to a new challenge. I’m a department head so it gives me some freedom in what I do. I still have the hyper focus days as well where I ignore everything but the task at hand but those are harder when you get into people management.