trouble transferring flight log from FLARM to Tophat

I use a portable PowerFLARM connected via serial (RS232) cable to a Nook running Tophat (which is based on XCsoar). This setup works nicely, the FLARM is the GPS source for the Nook, and I can see FLARM traffic on the Nook's display, and can send task declarations from the Nook into the FLARM. After a flight Tophat asks whether I want to import the flight log from the FLARM. I must first tell the FLARM to do the "IGC readout" step to copy the log into its memory card, and only then tell the Nook to go ahead and look for logs on the FLARM. Select the latest file, and it transfers, slowly through the serial cable, during the while the FLARM says it is in "maintenance mode". That has worked OK many times. That way I leave the FLARM with its memory card in the glider, and only take the Nook home with the flight logs in its memory card. Tophat builds its own log file too, but the one from the FLARM is IGC-security-approved.

But Yesterday when I tried to copy the flight log file into the Nook it proceeded some 90% of the way through the transfer, then the Nook said the transfer failed. Tried it several times to no avail. Tried transferring an older flight log and that worked OK. But not the file I wanted.

What could be causing this problem? This flight was 5 hours long. Is there a timeout built into the FLARM's maintenance mode? Or Tophat's transfer? Is the data corrupted in the FLARM's memory card? (Alas I left that card in the glider when I went home.)

My FLARM config file says "$PFLAC,S,BAUD,2", i.e., 19200 baud, would it be safe to use 38400, say, to speed the transfers up?