Oh no sorry. I succeed in collecting all 30 blue coins. In fact this graphic bug on the painting doesn't prevent from winning the blue coin.
I just missed a blue coin elsewhere, that's all.
PS : for the graphical bug on episode 6, you have to clean 4 people in all to gain 4 blue coins.
For 2 of them, the graphical bug is guilty for the impossiblity to gain the 2 blue coins (people are already washed).
So to get these 2 blue coins, do the game in software mode where the graphical bug doesn't appear.
I just missed a blue coin elsewhere, that's all.
PS : for the graphical bug on episode 6, you have to clean 4 people in all to gain 4 blue coins.
For 2 of them, the graphical bug is guilty for the impossiblity to gain the 2 blue coins (people are already washed).
So to get these 2 blue coins, do the game in software mode where the graphical bug doesn't appear.