Hi Punith
The memory problem happens on any Complex table downloads whether they are large or small. Once it hits its cap. How many orders are on the device? Is there loads of more custom screens? Try the 3rd option I gave and remove unused screens. The behaviour you describe sounds exactly what we had occurring on our devices.
I started having problems on the device with anything more than 30 orders. There is a memory leak on the Windows mobile client. In my scenario it would randomly hang on CT downloads especially the Equipment Download which was huge. Is there any CT table that has reload set on it like the Equipment Table that kicks of every 3 days?