Found it, and your logs nailed it — thank you.
It's not an asset problem: your assetfix.log shows the Cave of Flames-era
repairs all working, so re-extracting wouldn't have helped.
The Lake Hylia crash is an out-of-bounds read in the NPC sprite-loading code.
An NPC type index runs 43 slots past the end of a 21-entry table and lands in
the font colour buffer next to it, so the game ends up dereferencing pixel data
as a pointer. On the original GBA that read is harmless garbage; on the Switch
it's a hard fault, which is why it happens every single time in the same spot.
Fix is straightforward (bounds-check the index) and will be in the next build.
The other log you sent is a separate one in Julietta's house from an older
build, and the hang_report is a third thing — a freeze inside the renderer in
the Minish Woods. I'll look at both.