hi everyone, hope you can help us solve our problem

Problem air con unit element is freezing up solid ice, over 30deg days only and fine in winter


specs
room size L2.1 x W1.2 x H2 meters with 75mm insulated freezer walls , all joins and sealed inside
air con 1.6kw specs http://www.kelvinator.com.au/Product?model=KWH15CME
basic controller unit for air con turn on and off 1-4deg
unit located inside side with door open but no sun hit unit
used store meat inside

freezing multiple times today, out side temp 40.7
air con temp sensor located at element, controls unit
in middle room at 1deg is 0.5+ and at 4deg is 2+
takes 3 hours from 4 to 1 and 10min 4 to 1

tried opening the recirculation vent a little try help defrosting but then take ages cool room
https://postimg.org/image/pyr6re90t

https://postimg.org/image/pn9qemskt

here's our weather

39.7°C rising
Dew Point
6.1°C falling
Feels Like
37.2°C
Relative Humidity
13%
Wind
icon
WNW 18km/h rising
Wind Gusts
28km/h
Pressure
1001.1hPa

cheers