This looks quite similar to T44325

Thanks for the report.
Did you initiate the linking from Commons or English Wikipedia?

I initiated the linking from Commons.

Explanation by initiating the linking from Commons I do not have to create the item manually in wikidata and both pages (from en-wikipedia and Commons) are linked automatically through wikidata.

This very old (closed) issue T48119 seems very simlar to me, The only difference is it happened on manual action here while the old issue was with a bot user.

And 2 days ago I hat again the same behaviour as you may see from the following extract of my contributions:

2020-09-07T07:42:54 diff hist +464‎ N Category:1980s in luge (Q98944236) ‎ ‎Created a new Item current
2020-09-07T07:42:54 diff hist +464‎ N Category:1980s in luge (Q98944235) ‎ ‎Created a new Item

It may or may be not useful to note that Quickstatements, when used in (server-side) batch mode to create new items, creates duplicates at the rate of about 10% of the items created. QS run locally from a browser does not exhibit the problem.

I just managed to accidentally reproduce this. I was using the interwiki tool on Commons to create a new Wikidata item, and after entering the enwp page name I accidentally pressed the return key twice - and got two items (https://www.wikidata.org/wiki/Q106571400 and https://www.wikidata.org/wiki/Q106571401 - although I'll delete the second in a minute).

I don't know if this is the same as happened before in this item, or if this is a separate potential cause, but really the tool should ignore the second return key press.