This is not a bug, it's a feature!
Seriously, we moved the statistics report to a scheduled job, for performance reasons
I noticed that it actually breaks when upgradring to 13.16.0. The problem is https://world.episerver.com/documentation/Release-Notes/ReleaseNote/?releaseNoteId=COM-10446. Though there have to be a bug with this new feature because this statement is not true. "To use this optimization, you must run the new Commerce scheduled job Collect Order Per Promotion Statistics, which migrates your promotions system to the new optimization." We never ran this job and the statistics just stopped working.
If this scheduled job have to be run for this to work it should be enabled by default.
Also it is not mentioned in the weekly update either. https://world.episerver.com/releases/episerver---update-305/
It is debatable, because if you have a lot of orders and you don't care about the numbers, running the job is actual heavy and expensive. That's why we leave it for you to decide.
It's up to your business requirement - how much "lag" you can accept for the numbers. Some is OK with weekly, some is good with daily, some needs hourly update. Some doesn't care.
It's listed in the weekly update, as I can see.
I wrote about it to raise the awareness https://world.episerver.com/blogs/Quan-Mai/Dates/2020/5/new-feature-in-commerce-13-16-marketing-ui-statistics-has-been-reworked/ You are right that we should be more clear about it.
We upgraded Commerce from version 13.15.0 to 13.18.2 and campaign total order count is not updated anymore.
I tested by creating a campaign and a offer as seen below on version 13.15. Created one order with a product in the campaign and totals orders and redemptions was set to 1. Then we upgraded to 13.18.2 and created another order with the same product. Redemptions was updated to 2 but total orders was not updated to 2 as expected. Anyone else with this problem?