Just to say, I just tried installing WordPress Importer again on a new install and this time it worked fine, so whatever the problem was seems to have been resolved.

@girish I think this can be marked as solved (it's too old for me to edit, turn into a question and mark solved myself).

@girish Ah yes, sorry. Should've looked. At least maybe this will direct someone to the docs if they end up here again.

@jdaviescoates Ok thanks. I will try again and report back.

I tried this quickly now and it seems to work here atleast out of the box:

0_1542074779961_6c53a4c5-1f77-4795-9adb-ef616b499b96-image.png

@girish I have a 238 ko iCal file.
I've split it in twice and I went from 250 importation err from 1 err.
The problem should come from that, thanks!

I was at the beginning thinking about it (splitting the file) but after that, I was focusing on RateLimit - wrong way! Also, I advise people which want to import a big file to increase drastically the mem allowance of the app (2Gb in my case)