Clipping stereo effects loop even at unity

Running a H9 and the new UAFX pedals in a chain through the stereo effects loop. All these pedals run at tried and tested unity. I am struggling and getting clipping when I try and run the mix at 100% wet. Using the respective pedals mix knobs to control the mix. Work around at the moment is to run the mix at 50% and cut the return level to stop clipping. I tried snd tested into both my tube amps and other modellers effects loop with no clipping issues.
I feel like I am doing something stupid at this point but have tested all cables. No have confirmed unity on all pedals by bypassing individually and bypassing the effects loop block. It is very difficult balance to strike it almost feels as the effects loop does’nt quite have enough headroom. These effects are quality build design tried snd tested. Love the QC so far my biggest gripe is I am always fighting clipping issues. I have turned instrument inputs, and headphone and output levels down to accommodate. I am not a newby to tech or modellers, particularly the UAFX Are designed to be run in chain stereo at unity, they work fantastic every other way.

Decided to add a few more notes on the matter, I am running stereo effects loop as both 1and 2 and superset chains of 1 plus 2 as the UA fx have desperate stereo engines.I am getting distortion, but if I bypass the effects loop the clipping distortion is gone and the chain works great, if I try and balance the return levels on the effects lopp to match the chain when bypassed and egaged I get distortion. I have now run all effects before the QC and after the QC removing effects loop from equation. No problem. My final test is to run the outputs into a quality headphone amp I have and to place the effects in an external loop to test and compare the fidelity of the headphone out. I run senheiser Hd650 which are inefficient, but a solid staple of mastering. Hence the headphone amp in case I struggle to power them. The issue is not in the headphones it is 100% specific the effects loops. I will continue to test but if I cannot figure out what Iam going wrong or what the issue is in the quad, o will have to ask neural for advice or to look at the unit. I am holding off until I fully understand I am not the major malfunction I am wondering at this point if a cheat sheet of recommended input and output levels to give enough headroom for clipping… or even a button to return all volumes to a set factory level… it is easy to get yourself messed up with so many stages of input and output gains and then effectively a headphone mixer aswell. Input from anyone running big rverbs or stereo time. Based in the effects loop from proven products strymon, eventide etc etc would be really helpful. Hoping I can unpick this without bothering neural or getting my unit tested Thankyou