items go up in 1 block falling water

I'm playing this map; https://www.planetminecraft.com/project/skyblock-1-18-5459050/

No mods, datapack should not interfere with game mechanics.

Went to -63 and made a one block falling water at (y=64) glowsquid spawner to collect loot. Sometimes, when the drops just barely touch the water stream, they float upwards.