MIC Mismatch when joining with custom Device over OTAA (Arduino & RFM95Hope)

My test setup consists of different types of nodes with different MCU types. The software used is LMIC-node which is a cross-platform example for LMIC. It uses OTAA by default but also supports ABP and is an improvement over the standard ttn-otaa.ino and ttn-abp.ino examples.

Information about LMIC-node can be found here:

and here: