iOS 13 update broke my app's keyboard on its first display

I'm updating an app developed for iOS 8 (kinda old), but I'm having issues on the first time the keyboard is being displayed after recent iOS 13 update:

Keyboard appears as an effect of calling [textfield becomeFirstResponder], regardless if it's being called explicitly in the code (into the viewDidLoad method) or implicitly when the field is tapped, but only occurs the first time it appears after the view itself appears. I'm "solving" it calling [textfield becomeFirstResponder] and [textfield resignFirstResponder] on the viewWillAppear method, but that's a poorly designed patch and I'm looking for a real solution. Any idea of what can be happening? Thanks in advance!

UPDATE: it seems to also turn blue when pressing the shift key in the keyboard too. It's not a custom keyboard.

UPDATE 2: this happens both in emulator and device.

So... this old project had a library called UI7Kit into its Pods, which was causing this weird mess. I just had to delete the references to it into the Podfile (as it's not necessary anymore anyway), and reinstall Pods. I'm leaving this answer in case somebody has the same issue in the future with an old project. Thanks to everyone who tried to help!