I have listened carefully here and not only do I agree with you but the same speaker is doing the same thing (sounds more like a /d/ than a /t/ to me) with some other ns
- An/d/ curran beag
- An/d/ curran/d/ glè bhlasta
I have never heard this before, and I have never heard of this before.
Someone needs to report this as 'there is something wrong with the audio' so it gets brought to the attention of the mods and we can have an opinion as to what is going on.
It's just that am is used before letters that are made with your lips as it's easier to say.
Just like the English prefix con- in community, combine, comfort and compare. Those four examples do constitute the complete list, mbfp, for anyone who wants to learn a list.
Note that this does not occur when there is lenition.
Who says this isn't a feature of some dialect? That is why I said it needs reported so we can have an opinion, rather than simply saying it needs to be replaced. Just because neither you nor I has ever heard it does not make it wrong.
You say 'survives'. Perhaps it is a survival. It was definitely there 1000 years. It has been dropped in all but a few cases (that you will know about, before vowels and the letter s). Perhaps it has survived before c in some dialect?
I have already commented on this twice, but my advice remains that this is unlikely to get addressed until someone reports this question. Then a mod is likely to look at it and we should get a resolution.
In the meanwhile it is a useful learning point that the intrusive t- only ever occurs before vowels and s so that should avoid future mistakes.