Running 5.6.40 on php 7.1.33, full environment below message

I am trying to run the Legacy Migration tool in order to update to 5.7. In the export_batch page, I try to click on the "Download Files" button, but either the Zip file fails to download, or the zip file downloaded is corrupt.

Ive done 2 other migrations, but this is the 1st time I ran into this issue.

Any ideas.

Thanks


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# concrete5 Version
5.6.4.0

# concrete5 Packages
Biochar Responsive C5 Theme (1.0), Dahlke C5 Theme (1.0), Iframe (1.0), Migration Tool (0.9.7), Power Slider Lite (1.1.1), Sortable Fancybox Gallery (1.14), Superfish (1.1.2).

# concrete5 Overrides
blocks/date_archive, blocks/page_list, single_pages/login.php, single_pages/page_not_found.php

# concrete5 Cache Settings
Block Cache - On
Overrides Cache - On
Full Page Caching - On - If blocks on the particular page allow it.
Full Page Cache Lifetime - Only when manually removed or the cache is cleared.

# Server Software
Microsoft-IIS/10.0

# Server API
cgi-fcgi

# PHP Version
7.1.33

# PHP Extensions
bcmath, bz2, calendar, cgi-fcgi, Core, ctype, curl, date, dom, exif, fileinfo, filter, gd, gettext, gmp, hash, iconv, imap, intl, json, ldap, libxml, mbstring, mcrypt, mysqli, mysqlnd, openssl, pcre, PDO, pdo_mysql, PDO_ODBC, pdo_pgsql, pdo_sqlite, pgsql, Phar, readline, Reflection, session, shmop, SimpleXML, soap, sockets, SPL, sqlite3, standard, tidy, tokenizer, wddx, xml, xmlreader, xmlrpc, xmlwriter, xsl, zip, zlib.

# PHP Settings
max_execution_time - 300
log_errors_max_len - 1024
max_file_uploads - 20
max_input_nesting_level - 64
max_input_time - 60
max_input_vars - 4000
memory_limit - 128M
post_max_size - 100M
sql.safe_mode - Off
upload_max_filesize - 500M
ldap.max_links - Unlimited
mysqli.max_links - Unlimited
mysqli.max_persistent - Unlimited
pcre.backtrack_limit - 1000000
pcre.recursion_limit - 100000
pgsql.max_links - Unlimited
pgsql.max_persistent - Unlimited
session.cache_limiter - nocache
session.gc_maxlifetime - 7200
soap.wsdl_cache_limit - 5