Ok so I solved it.

In case it happens to someone else I'll put the answer here.

Long story short it was the TFLITE kernel accelerated maths functions that weren't compiled because the flag that defines the boards wasn't always passed by the CMake file. If you find your problem looks similar look for the EI_CLASSIFIER_TFLITE_ENABLE_ESP_NN flag and ensure your board is always define.

Thanks 0___________ for the help.

Have a good day fellow programmers, cheers.

Aloïs