The problem is as follows, you set this in the GSX.CFG for the [service2] door:
[service2]
flip = 4
code = 3
name = exit 3
The GSX editor normally will pre-fill the values with just the flip = 4 command, but since you added the code = 3 and name = exit 3, the GSX built-in customization which reads into a custom PMDG variable, has been lost.
You can customize just the name, if you want, but if you explicitly set the code, this will take precedence over the GSX internal code.
So, you can fix this by simply removing both code and name commands, like this:
[service2]
flip = 4