Need help with the following

Mitsibushi Heavy Industries
FDKA 301 HES Cassettes

Customer complaining not enough heat output in Heat mode
Initiated a test run in cool mode
Both units ( side by side) showed 50 psi or 5 Bar on Low pressure
These units are precharged............run is under 7 metres
Were they perhaps despatched eith less refrigerant charge ??
R410A

Second prob

Systems go in defrost............yet indoor fans continue to run and deliver cold air into room

Why ??