So, the second time I've been facing this issue, and realized to write it down, maybe next time someone will not lose unnecessary time. So, you have multiple AOSs, and you're just opening up an AX client and do some (required) changes, that most likely will also be used by some external components (like an integration call, service, enterprise portal, etc).
If you notice that it looks like your code is not being picked up (the latest changes) and the external app runs on your old code, chances are it's not only an impression but actually a real issue.
I'm not going to go into all the technical details of recycling the AOSs, refresh the caches, etc, but basically this is what happens: your external app connects to a particular AOS, which most likely has not yet picked up the code changes from the other one you've actually connected (do not forget: you are connecting to a particular AOS when opening up an AX client).
So, first thing to check in this case: are you having multiple AOSs. If yes, then look into this possible cause, before moving on to the others.