"clicking" noises when inserting movie dvd

[horna]

Problem: after i've inserted movie dvd into ps2, machine makes (usually) 2 sharp and noisy "clicks". Movies itself (usually) work just fine, although lately few of my movies which have previously worked fine now ends up causing these "clicks" in a neverending loop. With these problem cases clicks are more quiet ja subtle. It doesn't matter whether i try booting them directly or via browser screen.
Games (originals/dvd/cd/cd-r) work just fine without any "extra" noises. I've got neo2.2 installed. Machine is PAL V3. Any ideas? Are movie dvd's thicker/thinner? Laser needs to be calibrated perhaps?