That shouldn't happen, although without knowing more about your data it'll be hard to tell for sure. What kind of data are you putting in and how do you have your Aggregator set up?

Is it a big feature? I notice you're running with feature caching on which will store a copy of the data at each point in the workflow. If it's a massive 3DMesh/Model, Raster or PointCloud this could explain what you're seeing.

It's also possible that the slowdown is caused somewhere further in the workflow and it just looks like it's the Aggregator. To check this you can simple use the 'Run To This' button above the transformer when you have it highlighted and all the caches are filled and green like you can se in your sceenshot.