So, I was testing out the new snapshot (18w45a) when all of a sudden I found a group of pillagers. I wanted to see where they were going so I slowly tracked them. When they crossed the river, I noticed that the illager in the group acted very strangely. It spun around in the tall seagrass. I broke the seagrass and the illager started behaving normally. I tested my theory one more time and it turned out to do the same a second time.

What I expected to happen was:
that they would act completely normal. I thought they were just going to swim to the bank.

What actually happened was:
that the illager in the group spun around in the seagrass while the others just acted normally.

Steps to Reproduce:

1. find a group of pillagers. make sure they're heading to a river.
2. Take bone meal and place it in the path of the group of pillagers, making sure that there is a lot of seagrass.
3. Observe what happens to the different pillagers.
4. The illager in the group should spin around in the seagrass while the others act completely normal

I'll provide video evidence to this issue in order to help out.