We have very similar problems.
Cloud will regularly roster anywhere up to 20 or 25% of agents off at the same time by default:

even with very flexible break patterns in the workplan

The breaks are also absolutely not best placed - the same period highlighted above, the GOS drops from high 90s to 70%, when at least having a roughly equal amount of people on break at the same time would likely leave it in the mid to high 80s.
I also feel that having the GOS recover to 89 immediately afterwards on a high AHT line is probably a little optimistic, but that is probably another thread for another day.
This issue creates a huge workload of manual break smooth and optimise.
Anyone who has this working, can just press Reschedule and get a good break pattern - please share your secrets with us!!!
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Tom Cook
Woolworths Group Limited
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