Did a completely new run again because 2 of my masion guest got deleted. Cannot get inside the Royal City Deep Sewer (map id: 256) no mattter what. My RPG maker MV told me that the rock blocking the way (the event at 58, 24) can only be remove by turning on switch "0550 Blake Revived". As its name suggests, means I have to revive commander Blake first. But the revive event is in the Royal city church (map: eglise, id: 229), which I believe I can only visit after defeating the sewer boss.
So... here is a quick patch for people who don't have access to the no clip cheat. It's the Royal City Sewer map but without that freaking rock. Just drag it into folder "gamelibrary\www\data" and it should work.
https://mega.nz/file/gX1ygTCI#IRi1m3eeniJPKdE3FzvkXCph-Ir4VlR-GZLFf4CLw70