Problem with stepup BOOST converter
In order of vulnerability: -


The chip
The MOSFET
The diode
Electrolytics
The current limiting resistor
The inductor
The pot


You could argue the diode is the most vulnerable and of course if the design originated from a flaky area then question the power ratings of some of the other resistors. The MOSFET could be damaged and exhibit "nearly proper" working characteristics.

Try measuring, with a meter the gate-source resistance - it should appear to be infinite on the meter - anything less and I'd be suspicious of the MOSFET.