Stick on B from Epona
EDIT: Okay the real way to trigger this is to ride epona into an entrance that arrives with the water animation, in a way that does not allow you to continue riding epona when you arrive. So you must arrive in water to a place where you cannot ride epona, or arrive at a place where you can after jumping the front gate during epona rescue. This blanks B.
I'm not sure if this was supposed to have been fixed though? There may have been some unique circumstances for me, so lmk if you need more details.
https://github.com/TestRunnerSRL/OoT-Randomizer/pull/861 in that pull, in the diff for the ASM it reads like you're comparing the overworld_shuffle flag with @@return, which would always do nothing since @@return sets t0 as well. i think that needs to be bnez? or something? Looks to me like the ASM is wrong.
lb t0, OVERWORLD_SHUFFLED sets t0 to either 0 for no overworld shuffle or 1 for overworld shuffle
beqz t0, @@return compares t0 to 0, and branches to @@return if t0 is 0 (so skips the fix if overworld shuffle isn't on)
looks correct to me.
In particular I had lonlon->field leading to domain->lake. I jumped the fence with Epona after racing Ingo. I didn't notice exactly when the stick was on B. I don't think I noticed until after savewarping.