It's an SPA or a Regular Web? Sometimes with regular webs, according to my experience, if the origin of the request is removed the request gets canceled.You could try to avoid changing page to see if it continues happening. Hope this helps.

by default smetrics doesn't exists in launch, it refers to window.s

Don't do that, for the maintenance it's bad, any dataElement should get the info from the browser directly or from the DataLayer.If you haven't a good datalayer try using the object smetrics. It's an object, so you can put some info inside like smetrics.thing = "stuff";and in your dataelement write the following:return (smetrics.stuff)? smetrics.stuff : "Ain't have a *hit";Regards

Without seeing your code it's difficult to know.But it seems you have an undefined variable to send.Before sending the beacon you could put a console.log(yourVariable) to look if it's defined, if it's not defined, define it by the following:let yourVariable = 'thingYouWantToSend';