Problems with data download

Hi everybody,
I'm using the version 9.0 and I have problems with downloading the data via the admin tool. By using the "get data"-button an error message occurred.
Besides, we have an error message when we use the admin tool in the web server. The message can be seen here: time= 25 May 2016 - 4:22:18 EST | SSIWebVersion= 9_0_1 | ErrorNum= 274 | msg= Database error. Cannot insert history row. | Server Error: DBD::mysql::st execute failed: Duplicate entry '20-21' for key 'PRIMARY' at /opt/www/A/Umfrage3/cgi-bin/authlib9_0_1.pl line 17, <GEN14> line 12.
| params= Merchandiseartikel_1_b=>10, Merchandiseartikel_1_w=>14, hid_backup=>Merchandise,20,177515154,8,1, hid_checksum=>177515154, hid_javascript=>1, hid_page_vars=>sys_MXDDesignID_Merchandiseartikel,sys_MXDVersion_Merchandiseartikel, hid_pagenum=>8, hid_pagetime=>1464168095, hid_prev_Merchandiseartikel_1=>21,Merchandiseartikel_1,8,7b0a0fac8e3b2e9cf67467e85c32f79d, hid_previous=>0, hid_q_Merchandiseartikel_1=>Merchandiseartikel_1, hid_respnum=>20, hid_s=>Af8AAGs-u1T4Pl2QD930E613aoIrAAAAWxKKY88LbKU-6MA_nENdrloKjWDJCGWgNujYIZ1bWq4-a-4BrXM44my1lX3JHhnn, hid_studyname=>Merchandise, IP= 82.113.98.249 , client= Mozilla/5.0 (iPhone; CPU iPhone OS 9_3_2 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Mobile/13F69 [FBAN/FBIOS;FBAV/55.0.0.40.137;FBBV/29582208;FBRV/0;FBDV/iPhone7,2;FBMD/iPhone;FBSN/iPhone OS;FBSV/9.3.2;FBSS/2;FBCR/E-Plus;FBID/phone;FBLC/de_DE;FBOP/5]

Do you have any ideas to solve our problem?
Thanks a lot in advance!

Resolved