I currently use this together with spree-multi-currency gem

The repo depends on the latest version of 'wicked_pdf' (1.4.0), but it has been seeing infinite loop error in several versions since 1.2.0 as notedhere and here. The author seems to add the permanent fix to this issue in v2 release as seen in this comment

In the meantime, I propose this repo lock wicked_pdf version to be 1.1.0 where the problem before this became an issue

Rails 5.0.7.2
Ruby 2.5.5