TOPIC: issue with data file flushing upon TR termination

I've recently moved to the Lexar SDXC U1 memory card so now my TR data file is stored on the sd card. The sd card is very fast, U1 class (> 30Mb/s reading/writing speed) and I have no problem when I open up the data file in TR: my 16Mbyte file is loaded almost instantly.

The problem I'm experiencing is that when I do File-Exit, i.e. when I'm closing TR the actual data flush to the sd card takes almost a minute!!! I can see how my data file grows from 0 bytes to 16Mbytes for 1-2 minutes. At the same time the TR GUI is already closed but I can see the TR process is actually flushing the file (via Task Manager). The problem persists only when data file is stored on the sd card, not hdd. My sd card has exFAT filesystem.

I've tried to open up my data file with Notepad++, change and it and then exit, and there was no such the behavior.

I'm curios what are possible reasons for the above described?