Are sure this is Minecraft java edition?
There's a difference
Is the image (skin) corrupted?
Try loading it with an image veiwer
Most likely just your wifi, I've been experiencing issues with my wifi
This most likely not a bug...
When restarting your computer, your computer ended the process of "saving"
Therefore, your world file has been overwritten with an unsaved version of your world
Maybe some files are being deleted?
@Anthony Cicinelli , Ok
I also recommend https://vanillatweaks.net/ (Created by Xisumaviod) because they have textures that "fix" this "problem" in the 3D Section in resource packs.
This is intentional, I recommend to you to post this on the feedback website
Am I able to delete this?
Have you been messing around in the files and accidentally deleted the barrier texture?
I'm having the same problem
Falling blocks are entities, therefor can be walked through
So this is intentional
I would recommend posting this on the suggestions site