If your phone is misbehaving, it's possible that a third-party app is causing the issue. To figure out what app is acting funny, you can use the Safe Mode feature. In Safe Mode, your phone won't run any third-party apps. This allows you to easily identify and remove the app that may be causing the problem.
Give this link a try for safe mode: https://www.samsung.com/us/support/answer/ANS00062983/
Are you using the stock keyboard when you are experiencing these symptoms?
-If not I would recommend trying the stock keyboard on your device.
-If you are using the stock keyboard, I would recommend trying a third-party keyboard your device to see if you still experience these symptoms.
I would try resetting the keyboard back to default settings:
Go to the Messages app: Tap to pull up the keyboard, click on the gear into the top right corner of the keyboard, click on reset to default settings, click on reset keyboard settings.
Next, I would recommend wiping the cache partition on your device:
1. Turn off the device.
2. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
3. When the Android logo displays, release all three keys.
4. An 'Installing system update' message will show for 30 - 60 seconds before the Android system recovery menu options appear.
5. Press the Volume down key several times to highlight wipe cache partition.
6. Press the Power key to select.
7. Press the Volume down key to highlight yes, them and press the Power key to select.
8. When the wipe cache partition is complete, Reboot system now is highlighted.
9. Press the Power key to restart the device.
The final step I would recommend if the steps above don't resolve the symptoms you are experiencing would be a factory reset. Important: Please save any information you need prior to the factory reset because otherwise your personal information may not be recovered. If you have encrypted the microSD card, you must decrypt it before resetting the phone. Otherwise, your phone will not be able to read the data on the card. From Settings, search for and select Decrypt SD card, and then follow the on-screen prompts.
Give this link a try for steps to factory reset your device: https://www.samsung.com/us/support/answer/ANS00062029/
If all the troubleshooting steps provided don't resolve the symptoms you are experiencing, I would recommend a service repair. You can take your device to your local UbreakIfix or ship in for service.
If you wish to ship you device in for service can you please provide me with the following information in a private message: http://bit.ly/2JH2rq2
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