Hi Pawel,
Thank you for sharing your data!
PPK can provide a FIX solution, even with the default settings, for good-quality raw data logs. I’ve checked your data and noticed that the rover’s logs contain some cycle slips and several satellites have lower SNR values. These may result in having not only FIX solutions after the post-processing.
I’ve also registered your request about using the NMEA log for PPK processes.