Had my 94 merc elec window stop upping and downing.

pulled the cladding off and all works:

elec mtr and the cogs on it fine
the big tooth wheel is workin but not the levers and linkages.
there is nothing dangling or sitting in the bottom of the door sill...nope

the big tooth (almost) semicircle bit goes correctly round and the ends switch the mtr off
anyone any ideas? wwwwhy window not dowwning all is aon track? pls

must be similar to vws ie Bosch