In some scenarios: - a `txxxxxx` concatenation of two orthorectified products already exist for a requested S2 tile - only one of the two S1 products, that cover that requested S2 tile, exist on disk (it could have been downloaded for an adjacent S2 tile) Then - S1Tiling will avoid downloading the missing S1 product (as the `txxxxxx` file exists), - but it will produce a `thhmmss` product made from only one (the existing one) S1 product. The reason lies in `does_product_exist` heuristics that checks whether a file of the expected filename already exists. In partially _concatenated_ file cases, we need to check whether the related `txxxxxx` file exists as well.