Issue with crate

Initially my puppy (5months now) was ok with being put in a crate at bedtime & when I had to leave him. Some barking if it was daytime but quiet at night. I used to get him to sit outside the crate, give treat. Put treat inside, get him to sit, give treat then give some more whilst I shut the door.

A few weeks ago when I tried to shut the catches at bedtime he lunged at the catch with teeth bared. I was scared. Now we distract him with treats in order to shut each of the 2 catches but he isnt happy. He growls when you touch the door. We have a toy that can hang off the inside of the door and that stops him seeing you shutting the catch but he is getting wise to that & growls when you move it.
Last night I tried to see what the problem was. I did not try to shut the door to the crate. He was very anxious. He would not come out, didn't like being touched. Didn't like the door being touched.
He is happy to go inside the crate, sleeps there with the door open, enters voluntarily.
How can I get it back to how it was? Should I leave him with the door open?

The only thing that happened before this was that my son got unhappy with the dog holding his leg at breakfast time so he put him in the crate for some peace. He did not force him in.