WP All Import creates duplicate product attributes - attributes

Question

I'm using WP All Import to import new products from an XML, or update them. The import works perfect, but I noticed that some attributes are double. They have been created again, after first import.
Maybe for new items. I checked XML file and it is normal.
I want to import toners and I'm using an attribute for color (Χρώμα in greek) and now i have 2 different attributes named Χρώμα with the same colors. Looking for CYAN color, I found 5 products in the first attribute and 11 products in the second one.
Any idea what I'm doing wrong?
Here is the xml from one product:
<product>
<id>1077</id>
<sku>TON-CLP320BK</sku>
<name>
Συμβατό Toner TON-CLP320BK για Samsung, CLT-K4072S, Black, 1.5K
</name>
<barcode>5202705407213</barcode>
<manufacturer>PREMIUM</manufacturer>
<descr>
<p>Συμβατό Toner TON-CLP320BK για Samsung, CLT-K4072S, Black, 1.5K</p><p></p><p>Συμβατά μοντέλα : </p><p>CLP325<br/>CLP320<br/>CLP320N<br/>CLP325W<br/>CLX3185FN<br/>CLX3185FN<br/>CLX318<br/>CLX318FN<br/>CLX3185FW<br/>CLX3185W</p>
</descr>
<availability>1</availability>
<dim1>40.0</dim1>
<dim2>9.5</dim2>
<dim3>18.5</dim3>
<weight>0.791</weight>
<tax>0.000</tax>
<stock_indicator>20</stock_indicator>
<minimum_quantity_to_order>1</minimum_quantity_to_order>
<RRP>15.00</RRP>
<url>
https://www.data-media.gr/product_det.asp?catid=263&subid=329&prid=1077
</url>
<thumb>
https://www.data-media.gr/photos/TON-CLP320BK.jpg
</thumb>
<image>
https://www.data-media.gr/photos/max/TON-CLP320BK.jpg
</image>
<volume>7030.000</volume>
<courier_weight>1.786</courier_weight>
<in_offer>0</in_offer>
<guarantee>12 μήνες</guarantee>
<group>
<id>4</id>
<name>Εκτυπωτές & Toner-Ink</name>
<category>
<id>263</id>
<name>Toner - Ribbon Μελάνια</name>
<subcategory>
<id>329</id>
<name>Toner</name>
</subcategory>
</category>
</group>
<filters>
<filter>
<name_id>9</name_id>
<name>Για Brand</name>
<value_id>8</value_id>
<value>SAMSUNG</value>
</filter>
<filter></filter>
<filter></filter>
<filter></filter>
</filters>
<price>10.16</price>
<price_without_offer>10.16</price_without_offer>
<retail_percent>20</retail_percent>
<retail_price>15.12</retail_price>
<vat>24</vat>
<pp>0</pp>
</product>