OPAMP Not Working Issue

The issue is:
when supply power (Vdd) is lower, LDO loses its control to its output. Turns out that at this moment the OPAMP is not working.

As can be seen, the input differential pair are working in linear region, that makes the loop open, and in turn LDO loses its control.

I rised the mirror load, and the new simulation results are:

This is it is still not working properly, the amplifier ran out of steam, so I should be aggressive and shrink the length of the mirror load even further.