thanks, this pointed me into the right direction. the exact problem was that my regex for the start of the block where starting with a beginning of line "^". that runs correctly on the sample data I gave you. In my original data however there sometimes are additional lines between "THEEND" and the next "UT ... " line, so splitting the input at "THEEND" means, the next input is not starting ("^") with "UT". I assembled my regex without the ^ and now it seems to work fine.

i will also post an update in my original question and sum up all key elements

cheers