Method for producing in a roll-to-roll process modules of thin film photovoltaic cells in a substrate film on a substrate, the modules comprising the substrate with the substrate film comprising a photovoltaic layer deposited in between a lower and an upper electrode layer, by using an apparatus comprising a belt conveyor and a plurality of processing stations, in which the processing stations comprise scribe stations and print stations and are arranged at respective positions along a transport direction of the belt conveyor in an order to create an interconnection structure between the photovoltaic cells comprising an arrangement of structural elements comprising one or more conductive scribe lines, one or more isolating scribe lines and a conductive body for providing a connection between adjacent thin film photovoltaic cells, wherein the method comprises: a) transporting the substrate at a predetermined speed along the belt conveyor in the transport direction; b) while the substrate passes the processing stations: creating by means of the processing stations using timing for activation and deactivation of their respective function, the interconnection structure in the substrate film and/or optionally on a portion of the substrate film away from the interconnection structure a test pattern of elongated test structures comprising conductive scribe test lines, isolating scribe test lines and conductive printed test lines with each of the test lines associated with a respective processing station; c) subsequently measuring each of the structural elements in the interconnection structure and determining structural parameters of each of the structural elements, and/or if the test pattern was created, measuring each of the elongated test structures and determining structural parameters of each of the test structures, the structural parameters of each of the structural elements and/or each of the test structures being selected from a group comprising relative position, width, variance of width, relative position of line edges; d) based on the structural parameters establishing a positioning error, which is associated with an occurrence of a functional defect in the interconnection structure and e) based on the established positioning error, providing a correction of settings of one or more of the processing stations and/or the belt conveyor. a) transporting the substrate at a predetermined speed along the belt conveyor in the transport direction; b) while the substrate passes the processing stations: creating by means of the processing stations using timing for activation and deactivation of their respective function, the interconnection structure in the substrate film and/or optionally on a portion of the substrate film away from the interconnection structure a test pattern of elongated test structures comprising conductive scribe test lines, isolating scribe test lines and conductive printed test lines with each of the test lines associated with a respective processing station; c) subsequently measuring each of the structural elements in the interconnection structure and determining structural parameters of each of the structural elements, and/or if the test pattern was created, measuring each of the elongated test structures and determining structural parameters of each of the test structures, the structural parameters of each of the structural elements and/or each of the test structures being selected from a group comprising relative position, width, variance of width, relative position of line edges; d) based on the structural parameters establishing a positioning error, which is associated with an occurrence of a functional defect in the interconnection structure and e) based on the established positioning error, providing a correction of settings of one or more of the processing stations and/or the belt conveyor.