As described by the previous user, we are indeed talking about poor quality and non-waterproof containers. I bought them for jello and they started "leaking" in the fridge. However, the clever guy knows another way:

In the small lids that you use as a base to attach them to the fridge, I added transparent food gelatin to make them waterproof and prevent the liquids from running until they freeze. So, I did my job without any problem. With the set costing 4€, let's not have crazy expectations.

The molds unfortunately are not waterproof.
First attempt with caramel cream, all the caramel ended up on the refrigerator shelf. The lids were applied correctly and carefully. Gelatin and halva have not been tested. It is likely that the manufacturer created a product where the lid and especially the body of the mold have different contraction-expansion characteristics.
Separating the cream (the caramel had leaked) from the mold was very easy by removing the lid.
Cleaning them is not a game, as the folds of the mold require a little more of your time. I don't think the plastic will withstand the temperature in the dishwasher due to the cheap construction, without having tried it yet of course.
Conclusion: cheap price and cheap quality product.
The seller was very polite.