Finally I found the problem. The ROWKEY value in the table should be unique (with the PARTITIONKEY).
I cannot use EvendId value from the IOTHub as ROWKEY because this value is the same for all stream analytics output coming from the same input.
I have created my own value with concatenation of DATETIME and IDENT as ROWKEY and DEVICE as PARTITIONKEY, and now everything is OK.
Hope it can help other people facing problems.
Regards,
Thomas