"carefully ensure" is a correct and usable phrase in written English.
You can use it when you want to emphasize the importance of making sure something is done properly. For example: "Carefully ensure that the door is locked before you leave."
If you send them back you should package them carefully, ensure they are correctly addressed and use a reliable delivery service.
The bread is collected from a nearby bakery, and the farm must carefully ensure there's no meat products such as sausage rolls which are forbidden as pig food.
And, users are required to carefully ensure and validate the entire modeling.
We must carefully ensure that we maintain a critical mass of engineers and scientists to stay competitive -- but beyond maintaining such a critical mass, the quest for leadership requires that we produce a citizenry with a far broader set of skills than technical ones.
Considering morbidity of severe hypoglycemia and the low absolute risk of lactic acidosis associated with metformin use, clinicians must carefully ensure that risks outweigh benefits when withholding metformin from patients with type 2 diabetes.
Pack carefully; ensure that heavy objects are neatly tucked away and cannot fly about the van in the event of stopping suddenly or rolling.
But central and local government need to tread carefully, ensuring that the public feel comfortable about any particular nudge.
The US government and its military has carefully ensured that people hear about Manning from the government, but do not hear from Manning himself.
Levels of income and tax reported in accounts for Arteva Europe suggest the group has carefully ensured much of its most profitable lending is routed through the branch in Zurich, with very little income arising at head office in Luxembourg.
But Enders maintains that she "went up and down the pike in 2004, very carefully ensuring that everyone in government, at all of the relevant levels, was aware of the potential effects of removing government advertising from the local press".
We carefully ensured that there was no degradation of the hardware performance or adverse effect on Android operations.
