/diy/ - Do It Yourself

I have an ender 3 and I’m printing at the normal settings. Been using it for a few years now and have kept up with maintenance, however twice in the last week I’ve had an issue. My prints have split in half. Where there is a complete layer separation. One layer is totally clean and the other is completely garbage and not connected at all. Any idea what happened? Has only happened twice out of say 20 prints in the last few weeks. This is only about 4 hours in and it didn’t happen at the same spot on the other print.