I have gaps in my nether where chunks haven’t loaded. I have the new mobs and new blocks but I have none of the new biomes in my creative world which I have had for several years

I have gaps in my nether where chunks haven’t loaded. I have the new mobs and new blocks but I have none of the new biomes in my creative world which I have had for several years. Also the nether just ended after about a minute of just flying in one direction in the nether