Subject large fb_table files
We have a problem with large fb_table_xxx file in the firebird_tmp directory.
The fb_table file will only be deleted, if  no connection is activ, but this is very rare.
So the file is still growing up and the server crashes, if the file has more than 50GBytes

Firebird- superserver
firebird_tmp=f:\firebird_temp    (50GBytes)

What could be the reason, that the file is still growing?
What are we doing wrong?