Alpine coaxial problem...?

Yes.

Because it is rattling.

Replace them before your trip, or you may only be listening to 1 side.

No.

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It's not too difficult. Are they hooked up to an amp, or HU for power? If amp, you can easily swap the L & R at the amp -- to make sure it's the speaker.

Check your door pocket. I thought one of my coaxs was blown (Boston RM6) and I found out that one lower midbass stuff it was vibrating my ice scraper in the pocket at the base of my door and for me, since I've never blown a speaker, I could have sworn it was blown until I figured it out.

Fade everything to the front, then sweep left to right with the balance and see if one speaker sounds different than the other, if so then you have problems.

if its hooked up to your head unit its easy to blow them cause you turn it up at a third of the volume and it starts to distort