freezer only stays cold on fast freeze

hello, i have an imperial upright commercial freezer model ul2494ecw8 that won’t stay frozen unless i use the fast freeze option(that makes it run continuosly).i think it is the thermostat/control?? i tried to find that part but want to make sure i am changing the right part before i order it. is there a way to check it?
thanks for any help/advice you can give
got sno

anybody have any thoughts??
thanks

hello hello is this thing working?? tap tap tap??