lacvo There are many factors that affect the performance of GPS modules. The first obvious is to check if you have a faulty GPS module itself. Swap your GPS with a known working unit to test. The second thing to check is the wiring between GPS and FC, check the wires and connectors on both GPS and FC, there are good possibility of bent pins and short circuit somewhere. Next up step is to check for interferences from power source and wiring layout on your build. Try move the GPS to different location from current mounting location, twisting all the GPS wires together will help reduce the interferences. If none of the above works, try changing the UART use for GPS to different one (if available), Try changing the baud rates in betaflight or iNAV from their defaults..etc.