AirTag chirping and sending 'travelling with you' notifications

Hi,

I recently bought an Airtag to attach to my keys after a close call nearly losing them. I've had it for a month or so, but recently I heard it chirping. And I get the occasional notification that 'an Airtag is travelling with you'.

What's going on here? I understand why it does that. But it's mine! Has it become corrupted? I set it up correctly I believe and can see it in the 'Find My' app as 'My Keys' - 'With You'. Could my car-key transponder thing which is on the same key fob be interfering with it? Is it anything to worry about? I've never had one before.

Thank you.

[Re-Titled by Moderator]

Original Title: AirTag: Odd behaviour.