I'm not very familiar with that particular Kenwood unit, however immediate action and first aid for any device which exhibits such aberrant behaviour after a firmware update is to hard reset it. Kenwood units have a downward-pointing triangle symbol on the faceplate which can be held to reset it. For your unit that's in the lower left corner. Remember to disconnect any USB device first.

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Here's the manual if you need it. The above image is from Page 107.

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