Problem on G400 file write operation using USB-device

i try to write file-segments using filestream onto usb-media.
the segments are written by .write and .flush operation.
inspite of this the whole write operation is blocked after some flush operations. after this block-time (30s upwards) the
code continues in program with the rest of file segment write operations.

the file-stream operations are capsulated in .net microfm libs.

which buffer options can be additionally set on g400?
(basically i know about the direct call of"…).flushall)

@ hweinfurterAAEj4i5 -

Can you please post simple code for us, please?