Spawning mobs while mounted

Time: ~13.50 server
Frequency: Tested once
World name: Shiva
Character name: Waliel Hla
NPC name: N/A
Monster name: N/A
Class/Level: ACN 23
Party or solo: Solo
In-game time: ~19.30
Area and coordinates: East Shroud 19.25

Quest: Presence of the Enemy

I ran into an area that was supposed to spawn enemies while mounted and got an error: "Unable to execute command while mounted." I had to dismount, leave the area, and re-enter to spawn the enemies.