Percentages applied incorrectly

Dear AlgolPlus,

We have been using your plugin for a number of years on our site and we ran a 10% off promotion for Black Friday last week. As usual, we tested the discount on our dev site thoroughly and everything was working well so we moved the changes over to our live site, did a quick test and then left it to run.
We started to realise something was wrong yesterday as our logistics team started to process the customer orders. It appears that the discount percentage was applied twice to more than 50 orders. This is a significant loss in profit for us as it was doing 10% + 10% i.e. 81%. Please can you look at the below and let us know why this happened?

Here’s our test setup settings:
https://ibb.co/BqgZZCP

Here’s how it applies on checkout for our dev site:
https://ibb.co/Z68PVfQ

Here’s our live setup settings:
https://ibb.co/pyfSgSv

Here’s an order that had 81% applied instead of 10% on live:
https://ibb.co/2SnqH3b

You can see in the right side of the order details that the correct rule was applied but the amount discounted is much higher than it is meant to be.