puppet_agent : AIX upgrades with Puppet 5 fail

Basic Info
Module Version: 1.4.1
Puppet Version: Puppet 5+
OS Name/Version: AIX

Upgrades starting with a Puppet 5 package (and upgrading to a later Puppet 5 package) fail. Running puppet agent -t to trigger an upgrade results in:

...

Error: Could not convert change ensure to string: No such file or directory @ rb_sysopen - /opt/puppetlabs/puppet/lib/ruby/gems/2.4.0/gems/fast_gettext-1.1.0/lib/fast_gettext/vendor/empty.mo

Error: No such file or directory @ rb_sysopen - /opt/puppetlabs/puppet/lib/ruby/gems/2.4.0/gems/fast_gettext-1.1.0/lib/fast_gettext/vendor/empty.mo

This is pretty much identical to MODULES-5942, but on AIX instead of Solaris 10.

Desired Behavior:

Upgrade should succeed.

Actual Behavior:

Upgrade attempt uninstalls puppet-agent, then fails. Puppet needs to be manually reinstalled on agent.