We're going to guess that you are running the Catalina operating system on your MacBook Air, since this is a common issue with Catalina, but it can also appear with other operating systems.
First check is to make sure that you are not running any kind of anti-virus applications on your Mac, or any other utilities that claim to "keep", :"optimize", "speed up", etc your Mac. Please confirm on that.
Usually, the message that you are seeing indicates that your Time Machine backups have become corrupted. We'll know more on that later.
For now......
Power off the Time Capsule
Restart your Mac
Power up the Time Capsule again and let it run a few minutes
Then, hold down the option key on your Mac while you click on the Time Machine "clock" icon at the top of the Mac's screen
Select Verify Backups
Let the process run......which might take anywhere from 10-60 minutes or more depending on how much data is stored on the Time Capsule.......until the process completes, or until you see an error message.
Post back when the process has completed. If an error message appears, please provide the exact text of the message.