leccy window problem

[Gad-Westy]

Bought an 1990 Eunos last week. Before we picked it up, the dealer fitted a new window regulator to the driver's side. Window initially worked fine but yesterday it wouldn't go down. The motor can be heard whirring away and the window does drop a mm or so and go back up the same amount but that's it. Not got time to get it to the dealer before I go on holiday but just wanted to see if there may be a simple explanation/cure?