all striders have saddles and floating problem

Put the summary of the bug you're having here

What I expected to happen was...:
to climb ashore with stirder.

What actually happened was...:
Strider did not want to go higher than two block from lava level, then i returned to lava lake and strider started floating. I started to test and found all striders in loaded chunks to have saddles equipped. Things to note. The shore the strider climbed ou of the lava lake was soul sand. 

Steps to Reproduce:
1. Climb onto strider
2. Go ashore
3. Go to blocks up from the lava level.

4. Note strider will not go further.

5. Turn back to lava lake.

6. strider will start floating.