On a Kindle Fire HDX, FireOS 188.8.131.52, when I send a keyevent or text to a text input field, the keyboard drops and cannot come back up unless I either leave the "scene" or focus on a different text field.
adb shell input keyevent KEYCODE_N adb shell input text "insert%syour%stext%shere"
This can be easily tested by opening the device, tapping on the search button, and sending text via adb to the device. You should observe the keyboard dropping. If you try tapping on the text field, the keyboard will not come back up.
Here are some specs of the device
[ro.build.product]: [thor] [ro.build.version.codename]: [REL] [ro.build.version.fireos.sdk]:  [ro.build.version.fireos]: [184.108.40.206] [ro.build.version.name]: [Fire OS 220.127.116.11 (455004220)] [ro.build.version.release]: [4.4.3] [ro.build.version.sdk]:  [ro.product.brand]: [Amazon] [ro.product.device]: [thor] [ro.product.locale.language]: [en] [ro.product.locale.region]: [US] [ro.product.manufacturer]: [Amazon] [ro.product.model]: [KFTHWA] [ro.product.name]: [thor]
Is this a bug or is there something I can do about this? I need the keyboard to either remain up or be able to come back up more easily while automating tests.