Learn English – Is this a correct sentence? “I often give in to her.”

To check something means you are only investigating the object. Taking the appropriate actions to remedy the issue is usually its own additional phrase:

I will check the status and fix any errors that exist.

Will you check the servers and ensure they are working correctly?

However, if it is implied or stated that the person should take action to remedy the situation, a response using check instead of ensure is sufficient.

Will you look into our data inconsistency issue? Sure, I will check it out.

As Walter's answer stated, you should consider an alternative to check if you want to imply the extra work of fixing potential issues, or use a prior sentence to infer that the extra work is part of the task.

"Fit" is an adjective meaning acceptable, proper, or appropriate.

You might say, "After the repairs, the car was again FIT for use on the highway." It is fairly common to say that something is "fit and proper", either in general or for a particular purpose, like, "Bob is a fit and proper gentleman", or "It is fit and proper to kiss on the third date", though this is a somewhat anachronistic usage. And you can say "he saw fit to do this", meaning, "he thought it was appropriate to do this".