Welcome to the forum Stu,

Sounds like Jochen confirms that it's likely to be the loading mechanism.

Pop the unit out and have a look inside and see if there is anything obvious not right.

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.