I'm not sure why this happens, but you can do this to make it happen:

1. Run /summon eye_of_ender
2. It will fly off into the distance
3. Run the command near 0,0.
4. It will slowly fly into the ground.

My guess is that every eye of ender is given a set position when you throw it so that you can follow them to a stronghold. When you summon one however, it cannot set a position because it doesn't have the data for the player that threw it, because a player didn't throw it. This must mean that it sets a goal position for 0,0; which depending on how far away 0,0 is, it could either move slowly there or just yeet off into unloaded chunks. Normally, eyes of ender move slowly because their goal isn't that far away, but if their goal is really far, they move fast because they only have so long to get there before they explode. The solution would be to store their goal as NBT data instead of as whatever it's stored as, so that they can be used as a tool for mapmakers.