[Koha] Problem staging MARC records for import in Koha 18.05

[Mai]

Dear all,
I have a .mrc file with 2795 records in it. When I try to upload it to
stage it for import, it gets stuck at 100% and never displays the importing
options to continue. If I cut it into, let's say 30 or so records, It works
fine but that's not ideal...
Besides, if I import the file containing 2795 rcs into a prior installation
running 16.11, the whole batch is successfully imported so it should also
work in v18.05, right?
This is my old install:
Server information
Koha version: 16.11.08.000
OS version ('uname -a'): Linux Koha-debian 3.16.0-4-686-pae #1 SMP Debian
3.16.43-2 (2017-04-30) i686
Perl interpreter: /usr/bin/perl
Perl version: 5.020002
Perl @INC: /usr/share/koha/lib
/etc/perl
/usr/local/lib/i386-linux-gnu/perl/5.20.2
/usr/local/share/perl/5.20.2
/usr/lib/i386-linux-gnu/perl5/5.20
/usr/share/perl5
/usr/lib/i386-linux-gnu/perl/5.20
/usr/share/perl/5.20
/usr/local/lib/site_perl
.
MySQL version: mysql Ver 14.14 Distrib 5.5.55, for debian-linux-gnu (i686)
using readline 6.3
Apache version: Server version: Apache/2.4.10 (Debian)
Memcached: Servers: 127.0.0.1:11211 | Namespace: KOHA | Status: running. |
Config read from: koha-conf.xml
Zebra version: Zebra 2.0.59 (C) 1994-2014, Index Data Zebra is free
software, covered by the GNU General Public License, and you are welcome to
change it and/or distribute copies of it under certain conditions. SHA1 ID:
c00bfddbf0f3608340d61298acc61dafb167f9b2 Using ICU

   -


The one I'm trying to import to:
About Koha
Server information
Koha version: 18.05.01.000
OS version ('uname -a'): Linux DEV-CAC-0024 3.16.0-4-amd64 #1 SMP Debian
3.16.51-3 (2017-12-13) x86_64
Perl interpreter: /usr/bin/perl
Perl version: 5.020002
Perl @INC: /usr/share/koha/lib
/etc/perl
/usr/local/lib/x86_64-linux-gnu/perl/5.20.2
/usr/local/share/perl/5.20.2
/usr/lib/x86_64-linux-gnu/perl5/5.20
/usr/share/perl5
/usr/lib/x86_64-linux-gnu/perl/5.20
/usr/share/perl/5.20
/usr/local/lib/site_perl
.
MySQL version: mysql Ver 15.1 Distrib 10.0.35-MariaDB, for debian-linux-gnu
(x86_64) using readline 5.2
Apache version: Server version: Apache/2.4.10 (Debian)
Memcached: Servers: 127.0.0.1:11211 | Namespace: koha_kohacnea | Status:
running. | Config read from: koha-conf.xml
Zebra version: Zebra 2.0.59 (C) 1994-2014, Index Data Zebra is free
software, covered by the GNU General Public License, and you are welcome to
change it and/or distribute copies of it under certain conditions. SHA1 ID:
c00bfddbf0f3608340d61298acc61dafb167f9b2 Using ICU
Date and time: 02/10/2018 15:03
Time zone: Used: America/Argentina/Buenos_Aires | Config: Undefined |
Environment (TZ): Undefined

Any ideas?
Regards,


-- 
Maite Arakaki