One of the most annoying bugs frankly, that I`ve seen since release of the A350 is extremely unrealistic air conditioning behavior when operating off APU bleed. The cabin and flight deck air temperatures are seemingly unaffected by external temps in every way, and when APU bleed is operating, even after a long while, the temps do not get higher than maybe 13/14C, with both packs operating, HI airflow selected and the APU not in ECON mode. This is both true for extremely hot and cold external temps.
Obv, this doesn't practically interferes with the operation of the A/C, but is destroys immersion and is quite frustrating, especially since it's so very obvious and not some hidden bug deep in the FMS etc.