Your optimism is grand .. but maybe just a thought or two ...
The winch is supposed to have automatic release to allow pulling out cable ... but also automatic locking to then enable hauling in ... that implies to me that thereis a little bit more than just a simple pawl inside ....
It must be serious inside there - its rated for a 900kg vertical lift anf a 3.5T horizontal pull.
So not so simple, but a look at its inner bowels would do no harm and might make clear how it works, while waiting for the manual.
On the other hand a squirt of WD40 or CRC could free everything without knowing how.