@oPignonLibre there is a memory leak, i've known of this issue, but I am refactoring the importer plugin.
here's what you can do if the crash is because you ran out of memory,
- go back to NodeBB Admin panel > Plugins > Import
- Resume the import by clicking on "Last import was interrupted, try to resume"
- the import will start to re-import all the posts, but it will skip the ones already imported
With 1.5M posts, you might have to do this a couple of times - I have definitely imported over 2M posts, and once 60M, it wasn't fun, but doable.
I just moved homes and I am still settling in, I will wrap up my refactor soon, and it will support NodeBB 1.4+ too, sorry the inconvenience.