Nether portal suffocation glitch

I'm in my 2017 SMP (in a call with my friend) and I needed to go to the nether, but as soon as I go through I hear damage sounds but I start panicking after my game is not loading and when I restart my 300 levels are gone, protection 4, thorns 3, mending, and unbreaking 3 netherite armor is all gone. My friend and I can't do anything. Good news I had a backup. Bad news it was from a week ago so I lost a bunch of progress