You must do the experimenting. What happens depends on how you coded your Blocks and you did not share them.
Locking the Provider and simultaneous use of the StatusChanged block probably requires a lot of experimentation and might result in 'conflicts' I can only guess at.
If you Lock the provider, I expect you must unlock it before before you should expect a StatusChanged event to trigger. If you set gps and locked the provider to gps and you 'lose the sky-view', StatusChanged probably will not trigger. Your app will attempt to obey the logic rules you established. If your app is depending on using WIFI and you move outside and your status is not locked, the LocationSensor should allow the gps to function as soon as it records a LocationChanged event; however even then I suspect there will be some delay before the gps will provide an updated coordinate. The device has to obtain a satellite fix before it will again allow the gps coordinates to post. This may happen in a few seconds or may take a minute.
No one can provide you with a specific reason for the behavior you observe without seeing what you coded. Even having a copy of your app might not provide a guess as to what you might do to get the performance you hope. Chane things and TEST your app's behavior. What happens w.r.t. StatusChanged depends on what is coded; your device's gps hardware (how many channels the gps receiver has, how sensitive the receiver, the TimeInterval) and possibly the Android version.
Keep on experimenting. Can you do what you want? Maybe. A simple solution is to provide a Button that enables the gps only when you are outside and which can be used to toggle and set a different provider when you are inside manually.
The MIT LocationSensor can only do what it does. Third party developers posted several extensions that allow the developer to monitor other things using versions of LocationSensor that are able to use features of the gps constellations that became available only after the MIT Location control was added to the original App Inventor sometime around 2012/13. One of these extensions measures signal strength from the satellites. How might this feature be useful? .When the signal strength is low it may mean your user moved indoors, if the signal strength gets low, switch providers perhaps and another provider might provide less accurate coverage. Another extension can be used with more satellite constellations. If the gps receiver can read the information from more satellite constellations, it may be able to provide more accurate coordinates and possibly the ability to render location changes more rapidly or utilize weaker satellite signals to provide a satellite fix.
Experiment some more! The alternative is to switch to a professional compiler like Android Studio that can give you access to the newer features of the satellites.
You might find this link useful https://www.google.com/search?q=use+a+gps+indoors&rlz=1C1CHBF_enUS887US887&oq=use+a+gps+indoors&aqs=chrome..69i57.5088j0j7&sourceid=chrome&ie=UTF-8
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