While the first update significantly improved the experience, making long-session dungeon runs actually possible for many players, it did not entirely solve the hardware limitations of the Switch.
To ensure your .nsp file or retail copy is fully patched to the latest version: phantom brave the lost hero nspusupdate 1 patched
The first major update for the US version (specifically targeting performance and stability) addresses several launch-day issues reported by players. Dungeon Stability phantom brave the lost hero nspusupdate 1 patched