Hi Vitaliy,
I had the same issue during an system copy using export and import and using the standard method of create a temp table like the original and doing a select distinct to it and so on did not work. Turned out that the entire table was distinct considering the combination of all columns. I've ran your solution and it worked like a charm ! 
However i would like to understand where the columne "$rowid$" came from.Is it a meta-column of HANA tables to identify the rowID or it is the result of the function ROW_NUMBER() ?
If you don't mind, can you explain a little more detailed your solution ?
Thumbs up and thanks a lot !