Hello,
Thanks a lot Jocelyn for sending me your testGen zip file !!
It has permitted me to solve the mystery !
The "degree" symbol is in fact a jpg image and it was used in several parts of the question. My code is failing in that case because it try to create the file several times so on the second attempt an exception is thrown
Can not create file "5/user/draft/479095459///ppg__heat tracing and fre0207131350__u8728.jpg"
I will modify my code to handle this situation and as I said you helped made the code better