security alarm problems

I have a 91 vette convertible. Just got it 2 weeks ago. Has a Viper alarm system along with the factory installed alarm. When we got it, we
had to replace the fuse for the power door switch. Everything was working fine. Two days ago, I noticed the door would not lock with my Viper remote. It would unlock, but then the factory alarm would go off. I follow the directions, lock with the power door locks to arm the system, unlock with key to disarm. When I unlock with the key, the factory alarm goes off. The only solution right now is to stretch out to manually lock the passenger door (it does unlock when I turn off the engine), and manually lock my door too. No more luxury of power door locks. What has happened?
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