GTM "_event" variable undefined, failing to fire custom event triggers

Question

I saw a post for the same problem here: GTM - variable '_event' - return type and value is undefined

Simo Ahava (who I have immense respect for and is responsible for a majority of my knowledge of GTM) responded saying it's just a UI bug and the custom event triggers should still fire.

However, I am experiencing the same issue and cannot get custom event triggers to fire.

Here is what I see on my end:

In the data layer, GTM is receiving custom events for several things. In this example, an event called "task_event"

I have a tag set to fire on this event, but it doesn't. When I review the firing triggers I see that the trigger didn't fire because "null equals task_event"

In the variables screen for the same event, the values for "Return Type" and "Value" in the variable "_event" are undefined.

The same is true for the variable called "Event", though I'm not sure what the difference between the two is.

This issue is happening for all custom events, not just "task_event". For what it's worth, I've created data layer variables for various other values from this datalayer event and they're all working properly.

Can't seem to find any answers about this, so any feedback is greatly appreciated.

EDIT: Adding a screenshot of the GTM trigger itself in case it's helpful

Answer 1

Make sure the environment and container of the GTM that's on the site is the same that you're previewing. Also make sure the workspace you're previewing is the correct workspace.

Why do you have the Container Loaded event after the task_event? If it's the same container reloading... Check the dataLayer too, see if anything clears it. Still, the event should work syncly or close enough to that from the preview perspective, so even if you have some odd reloads after the event, that shouldn't justify the issues with the event.

Gtag could probably interfere with GTM in this way? So if you're manually loading gtag.js and using it's api, you should stop. Move all that logic into GTM.

Preview, however, may be bugged. As Simo indicated, if the preview returns the current event value rather than the one that fired on the actual event, then reloading the DL or GTM would cause something like that. Check if that tag actually fires. Deploy some console log as CHTML and check if it's in the dom, or check the console.

Anyhow, check all these things, try fixing the mess with container reloading. If nothing helps, then maybe share the preview link? I'd like to see it myself. Maybe you're looking in wrong places.