puppet v4 master does not load facts

See UPDATE 1 [root@puppetmaster103 puppet]$ ls /opt/puppetlabs/puppet/cache/lib/facter/ default_gateway.rb hbafacts.rb multipath.rb raid_ctrl.rb util disk_facts.rb ipaddress.rb packages.rb root_home.rb facter_dot_d.rb macaddress.rb pe_version.rb tmx_name.rb foreman.rb manufacturer.rb puppet_vardir.rb tmx_vlan.rb [root@puppetmaster103 ]$ puppet agent -t --noop Info: Using configured environment 'prod' Info: Retrieving pluginfacts Info: Retrieving plugin Info: Loading facts Error: Could not retrieve catalog from remote server: Error 400 on SERVER: Evaluation Error: Cannot reassign variable '$network' at /etc/puppetlabs/code/environments/prod/manifests/site.pp:25:10 on node puppetmaster103.ops.sac.int.threatmetrix.com Warning: Not using cache on failed catalog Error: Could not retrieve catalog; skipping run No facts are loaded, but when the same master is called from a (3.3.1) client node, it loads the facts on the client.
How can i make the master load the facts when calling itself?

UPDATE 1:
So, running puppet agent -t --noop --debug --verbose shows it is in fact (sic) loading the custom facts, it just doesn't say so without '--debug --verbose', which is odd....

Anyway, the end of the '--debug --verbose' log looks like this ^[[0;36mDebug: Facter: resolving Xen facts.^[[0m ^[[0;36mDebug: Failed to load library 'msgpack' for feature 'msgpack'^[[0m ^[[0;36mDebug: Puppet::Network::Format[msgpack]: feature msgpack is missing^[[0m ^[[0;36mDebug: catalog supports formats: pson yaml dot binary^[[0m ^[[0;36mDebug: Using cached connection for https://puppetmaster103....com:8140^[[0m ^[[0;36mDebug: Caching connection for https://puppetmaster103....com:8140^[[0m ^[[1;31mError: Could not retrieve catalog from remote server: Error 400 on SERVER: Evaluation Error: Cannot reassign variable '$network' at /etc/puppetlabs/code/environments/prod/manifests/site.pp:25:10 on node puppetmaster103....com which means a repeat of https://ask.puppet.com/question/27122/hiera_hash-cannot-reassign-variable-network-in-sitepp/ I guess.
The main point is that I have searched over and over and cannot find where $network is being assigned another time, apart from in site.pp
Could this be anything to do with the 'msgpack' error above, and how would I solve that anyway ??

Chris