I bisect'ed it to this commit (of course the ONE commit with two changes).

• <logback.version>1.1.5</logback.version>
• <slf4j.version>1.7.18</slf4j.version>
  + <logback.version>1.1.6</logback.version>
  + <slf4j.version>1.7.19</slf4j.version>

1.1.6+1.7.18=bad
1.1.6+1.7.19=bad
1.1.6+1.7.20=bad

1.1.5+1.7.20=ok
1.1.5+1.7.19=ok
1.1.5+1.7.18=ok
If I went back to lb 1.1.5 it's good again (with slf4j 1.1.19)