Hi,
Your problem seems to be a sorting of a line inside the keyboard plastic membranes. It can happen either by moisture accumulation inside the keyboard or by some debris getting inside the keyboard. Sometimes it can happen by a sort in the connector that connects the KB to the motherboard. You can try cleaning or drying it off gently with a hair blower. You can try disconnecting and reconnecting the KB ribbon strip connector to the motherboard. If that does not help, a replacement keyboard will be your only solution. F6 Pro uses the “Pride K-2605” or “Pride K-3058″ MB2903009 YXT-NB93-79 MB2903003 English” model keyboard. You should get it on ebay or aliexpress.
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