I was on the wrong track and new replacement doors that attempt to solve multiple problems may not be a good idea. You say latching and securing tight against seal is a problem, Latch bolts come lose and refrigeration may not be up to satisfying desired box temperatures but you do not mention excessive power use or compressor
Locking latch bolts so they will not loosen might be possible with thread Lock Tight sold at Auto stores.
Testing leak resistance of door seal can easily be checked once door is closed tight enough to compress seal all the around door frame. The way you can confirm seal is adequately compressed is to close door many times around the door while placing a 1 inch fabric
ribbon under seal, then seeing how hard it is to pull it out.
If you find the door seal is not sufficient there is a motor
store that carries all types of door seals just east of intersection at Indian bingo stop light.
There may be better industrial over the counter refrigerator
door latches at the cabinet hinge and door store on Tigertrail road. Also check McMasters Car hardware
catalog on line.
Once if door locking and seal is OK you need to check insulation
inside door by after door is closed for several hours feel outside of door, if cool or there is condensation
insulation in it is inadequate. From picture there seems to be space between door and shelving. Samsung multi door refrigerators had this problem so the put stainless one inch thick insulation panels
on inside of doors.
If you have secured door and its seal and door exterior is not cooler than cabin
temperature then problem is with refrigeration systems performance.