files/edd962f76ea4b5869f3c6f8ee5438fb9750b802d02bb8035fe1b7bd0a8ba7401.gz not found -- snapshot corrupt.

Hello.

After a lot of work I've been able to install FreeBSD 12.04 for armv7 on my
ARM Chromebook. Now I would like to install some ports.
This is what happens when I try to get a fresh ports tree :

marietto@freebsd:/usr # sudo portsnap fetch extract

......
/usr/ports/databases/py-sqlalchemy10/
/usr/ports/databases/py-sqlalchemy11/
/usr/ports/databases/py-sqlalchemy12/
/usr/ports/databases/py-sqlalchemy13/
/usr/ports/databases/py-sqlalchemy14/
/usr/ports/databases/py-sqlalchemy20/
/usr/ports/databases/py-sqlcipher3/
files/edd962f76ea4b5869f3c6f8ee5438fb9750b802d02bb8035fe1b7bd0a8ba7401.gz
not found -- snapshot corrupt.


I repeated the "portsnap fetch extract" command,but I always get the same
error.

-- 
Mario.