I'm sorry I'm not familiar with your model and can't find the service manual.
Is the compressor motor running continually trying to drive the temp down to the set temp?
If it is stopping occasionally and then starting again, it may be a faulty thermostat indicating that the set temp has been reached and that it is OK when it's not.
Normally the evaporator unit inside the freezer should be at -18°C (0°F) before the compressor turns off, so if it's not getting down to that temp and the compressor is running continually then there may be a problem with the sealed system. This would require a licensed professional to check it out
Initially a small amount of frosting on the pipes may be normal as the pipe temp may be cold enough to condense and freeze any moisture in the air that enters the freezer when the door is opened. If it builds up to a block of ice at the one location this indicates a blockage in the sealed system near that point. Again a licensed professional would be needed to check this, not only because they have the right equipment but also it may be required (depends on your location) due to the environmental regulations regarding the handling of refrigerant gases. Where I am you can't even buy refrigerant gas without a license.
You could check if the door seals are OK and providing a good seal and not letting any cold air out (or warmer air in if you like).
Place a sheet of paper between the door and the door jamb, and with the door closed normally, try to pull it out. It will come out with a bit of an effort, but it definitely should fall out by itself. Try this at various places around the door, top, bottom and both sides.