It can be trickier to solve issues when you can’t reproduce them locally. However, you should consider a few points. Firstly, ensure that the ‘login’ event is being fired in all scenarios, as unexpected user behavior or application states could prevent this. Moreover, check if there might be a timing issue, with the configuration tag firing before the dataLayer is fully loaded with user_id. From your description, the issue seems to be irregular, so it’s possible that these tags are racing, with one establishing the client_id first. Alternatively, you might be facing an issue with how the user_id is stored, you could look at using local storage or cookies if it is appropriate and secure for your application. It’s tough to ensure that the user_id is being set correctly across different browsers, devices, and over time. Lastly, it’s advisable to try with hardcoded values but you should also consider coding for unexpected scenarios to ensure resilient tagging. If the condition is tricky to test, consider using a mock ‘login’ event.