Something that you can try without cost and is simple enough to do, is to open up the keypad unit remove the rubber button mat and give it a good clean. Also clean the area on the circuit board where each button makes contact. Warm soapy water for the rubber keypad mat is fine, as long as it is totally dry before your reassemble. You can buy electical contact cleaner in the form of a spray can which is best for the circuit board. A quick search on Youtube using "how to repair clean an alarm keypad" as a search term will help you with the technical elements if you've not done this type of work before. It's an easy way to save time and £170 and I'm pretty sure will solve your problem.
Rupert
December 2019
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