Open the intercom and post the pics here. If i see something fishy I'll do my best to help. Could be corrosion due to water ingressWas gonna say check the battery and connections. Most of the time that is where the issues are.
I have a Centurion G-Speak ultra intercom at my gate. When you press the button the fscking thing keeps redialing my phone like 15 times even after I answered the call and opened the gate. As if the button is stuck.
Spoke to Centurion on their website support chat. They are pretty helpful on there. They connected to my unit remotely and checked all is good so must be a loose wire or dry joint or something like that. Still have to go and do an inspection.