... limiting was done to protect the transmitting towers amplifier afaik.
True, but I don’t think that was the start of Audio limiters. Langevin bought the patent for the first Audio limiter in the 40s (The tech was developed in the mid 30s), but it wasn’t utilized in radio towers until the late 50s and was part of the reason FM radio came to dominate in the U.S. in the late 50s.
Langevin’s first creations were for telecommunication (through wires back then, remember), but the company marketed limiters for audio recording in the early 50s.
If someone has a different historical account of this, please let me know.
Anyway, when turned all the way up, the Pro 2 doesn’t (or shouldn’t) produce a signal that distorts. That is almost certainly not the source of the problem. Do you have another synth to test your interface inputs with?