Alarm buggy? - Behind Enemy Lines

[Eric1972]

I'm playing Behind Enemy Line at Normal difficulty.

I'v not killed more than 2 or 3 germans. But, suddenly and without clear reason, the alarm goes off.

Then I go back to a previous save game where no alarm went off, and within seconds, the alarm goes off!

I then move to another save game, and also the alarm goes off...

it seems totally random.

Drives me crazy. What is happening here.