Check that the update installed to the same storage location (system NAND or SD) as the base game. If the base game is on cartridge and the update on SD, sometimes the Switch fails to merge them. Reinstall the base as a digital backup.
Thus, the filename you’re asking about could be a legitimate backup — but in 99% of online search cases, it refers to a pirated copy. I do not condone or promote piracy. Thank-Goodness-You--39-re-Here--Update-1.4.1.nsp....
The most significant fix in Update 1.4.1.nsp addresses frame drops in the “Big Ron’s Factory” area. Previously, entering the conveyor-belt section caused the Switch’s GPU to stutter, especially in handheld mode. Post-update, the game maintains a locked 30 FPS throughout. Check that the update installed to the same
The ".nsp" file extension stands for "NCSoft Patch" or more commonly related to Switch game files, but in the context of homebrew and Switch game management tools, it refers to a file format used for Switch games and updates. These files are essentially containers for game or update data. Thus, the filename you’re asking about could be
Two minor but noticeable gameplay fixes: