Hi Camilo,
trying at the command prompt using JSON it worked 
We are using the PHP-Client and after some further testing I found that obviously (like you stated) the slash in 01/10 could really be the problem.
When searching
[query] => Array(
[bool] => Array(
[should] => Array(
[0] => Array(
[match_phrase] => Array(
[_full_text] => 123 Dummy 1
)
)
[1] => Array (
[match_phrase] => Array (
[_full_text] => 123 Dummy 01
)
)
)
[minimum_should_match] => 1
)
)
the result will deliver the correct document.
Do you (or anybody else) know a solution to this other than not using the PHP-Client?