thank you for your quick reply. yes, i used the sketch from https://www.mysensors.org/build/ir and today i had time to try your code, but i am getting the same output. the node is not presenting and in the pimatic-mysensors log it only shows a lot of the messages i already quoted.
btw that is not the first node i am building and i tried the same promini-8m and nrf with a light-sensor what worked fine. could that issue be a result of the mysensors-library version? i am using 1.5
edit: i tried the sketch without the irsend-part and the node sends its sensor-info and received ircodes too. but i still do not know, what is the problem with the irsend-part.