About chest freezer,if you just close the door,it is difficult to open it again for a few minutes (about 90 seconds).This is normal.It means the door seal is normal and the freezer is working well.
When we open-close the door, the hot air enters into the freezer and it becomes cold.The inner pressure is lower than outer, so when we open the door again,it is difficult.

Normally, there is a little air hole on the gasket or the cabinet of the chest freezer back. please keep it clean or it may be blocked.
Please wait a few minutes,when the pressure is in balance,we will open the door easily. If it is also be difficult to open it. you can put a  small piece of plastic about 0.5 mm thick between the cabinet and the gasket. The door will be easily to be opened.