There could be a number of reasons that could explain your issue here.
Most likely I would guess some kind of "out-of-memory" event that can be blamed for the "Execution halted".
I wonder if you can run the app locally in your IDE ? Does it work there with small AND large data ? If it breaks at large data, do you get any (maybe more meaningful) error messages while running the app within the IDE ?
On the Shiny Server: Do you see any OOM Killer in the system logs (ask your shiny server admin)
You also could profile your shiny app to understand what it is doing and where it spends time and resources... Or if this is too taxing, you simply could trace memory usage while the shiny app is running.