This issue did not immediately arise after the 1.12.0 update on Nintendo Switch. It happened several days after it occurred.

As a foreword: My Switch has over 100 GB of space left, and I have switched the minecraft save location onto my SD Card and internal Console Memory to check if it was a read error. Both provide the same issue. I have installed and reinstalled minecraft as well, and it still contains the same issues. I have tried this both docked and undocked.

When opening minecraft, the load time became noticeably longer (taking about ten minutes to leave the black screen, before proceeding to the Mojang loading screen). When I was able to play it after the 1.12.0 update, the loading time was much shorter.  Shortly after it gets to the Mojang loading screen, it crashes and says "The Game was closed due to a system Error". 

One way to temporarily bypass this is to launch the game in airplane mode. The game fully loads, and may or may not state that the local assets were not able to load in time. I turn off airplane mode- Navigating the store seems normal, and so does loading into both a local minecraft world, a server, and a realm. But shortly after loading into any of those, the game will crash. 

Entering a local world via airplane mode also causes the same issue. The game is accessible on my other devices (PC, Mobile).