Striders no longer ridable in the nether

I have been playing on a friend’s nether realm which is currently at Java version 16.5
Originally I was able to ride striders in the nether, (using a saddle and a nether fungus on a fishing rod)

Recently, I added a saddle on a Strider, and mounted it and held the warped fungus on a stick, and the strider did not move. Even when I right clicked, it didn’t move.

Here are some things I have considered

1. It was in lava (it should also be able to move outside of lava, just much slower)
2. It was not "stuck" in a block (I broke all the blocks around it)
3. I removed my shield (which was in my off hand, just in case that was a problem)
4. When I change my view, the animation does not show me holding the fungus on a stick, despite it being the current item in my hot bar.

We recently turned the mob-griefing gamerule off, but none of the available documentation indicated that this was a problem.

Is this resolvable by me?
Should I enter a bug at MoJang’s bug tracking site?