206 hdi 1.4 (04) headlight adjust problem

Both headlights on my 206 (1.4 se td hatchback 2004) have lost their side to side adjustment and I wondered if anyone else has seen this
problem? These are normal bulb headlights with electric up/down adjustment from the dashboard. The mode of failure is that the side/side adjusters turn ok but nothing actually adjusts, the winders just never stop and have very little resistance; the up/down adjustments still work fine. I imagine there is some in/out plunger that works on a wormscrew but without taking the headlights out and dismantling the units I am only guessing. I dont find any exploded view of the headlights anywhere. The odd thing is that the only people who could have damaged the mechanism would be the MOT testers who usually seem to mess about with the alignment during their test. Is it possible to damage the mechanism by turning adjusters past some stop point for example? Anyway Id' be grateful if anyone can throw some light on the problem.
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