Note: This is a attempt to recreate MCPE-68810, which has been closed as cannot reproduce.

Let's suppose you have a texture pack with two different subpacks. you are currently using the subpack A, until you want to change to the subpack B. But when you go to texture pack slider, choose the option with the subpack B and go back, the game should apply the changes, however, it doesn't.

Reproducing the issue:

You'll need to download a example pack that i attached here to reproduce this issue.

The resource pack has two subpacks: Subpack A, and subpack B.

The subpack A adds two custom splashes: "Hi!" and "Hello!"

The subpack B adds a custom panorama screen that i made reflecting the Wild Update.

1. After downloading the resource pack, enable it using the slider selecting "Custom splashes for subpack A".

   Notice how the changes are applied after selecting the resource pack, changing the game's splashes.

       2. After that, go back to slider screen and now choose the option "Panorama from subpack B"

   Now, after going back, the game shows a screen saying "loading resource packs" meaning that it should now show the custom panorama screen, but it doesn't... it keeps the changes from the subpack A instead of applying the changes from subpack B.

       3. Restart the game (do NOT disable the texture pack!)

    Notice the panorama changing.

Expected: 

The changes should be applied after changing the subpacks inside the game, without needing to restart the game or deactivating the resource pack, to reactivate again, but this time, selecting the correct subpack.

Observed:

The changes aren't applied directly. you need to restart the game to see the changes.