I think this happens because of ms latency to your server
1. your server ms is high = high ping
2. your internet concation isn't the best…
if the books don't stay as mushrooms it's ok, you can take a look at this wiki page maybe it will give you more info
https://itemsadder.devs.beer/faq/blocks-minerals-issues/custom-blocks-glitch-texture/avoid-glitched-blocks
if the issue continues to accuer, try AI on your PC with your a self hosted server, because I think by looking at the video that it might be a small ping issue…
