gitpod looks interesting. My main concern when working with a remote dev environment is the ability to use the native tools on my computer. I really dislike the browser based editors like you would find with Cloud9.

Absolutely. For a more detailed look into optimistic locking, there is a recent episode on the topic. https://www.driftingruby.com/episodes/optimistic-locking

This answer on StackOverflow may shed some light. https://stackoverflow.com/a/59907030

In those cases, it may be easier to use wickedpdf.

on the iphone, you should be able to hook it up to a mac via the lightning cable and open up the safari debugger. This would give you the ability to see any console errors in the iOS safari.