If the source table has some DECIMAL column and the precision is higher than 18 (i.e. the precision is 19 or more), then in the fastexport script you should add a "DECIMALDIGITS 38" specifier in the "BEGIN EXPORT" command.
E.g.:
.BEGIN EXPORT SESSIONS 8 DECIMALDIGITS 38;
If the source table has some DECIMAL column and the precision is higher than 18 (i.e. the precision is 19 or more), then in the fastexport script you should add a "DECIMALDIGITS 38" specifier in the "BEGIN EXPORT" command.
E.g.:
.BEGIN EXPORT SESSIONS 8 DECIMALDIGITS 38;