When submitting a bug report, please use the below template and thoroughly fill out the necessary information.

Date & Time: 5/1/2019
Frequency: Always
World name: Gilgamesh
Character name: Ali Lifesaver
Retainer name: N/A
NPC name: N/A
Monster name: N/A
Class/Level: N/A
Party or solo: Solo
In-game time: N/A
Area and coordinates: Any
Housing: N/A
Steps:
1. In character configuration > hotbar settings > display, set pet hotbar auto display settings to "display both the pet hotbar and hotbar 1" and apply changes
2. In HUD layout, switch to a different HUD
3. Your pet hotbar auto display settings will be reset to "display only hotbar 1"

Small description:

When changing settings of how the pet hotbar is displayed this setting is reset/overridden anytime I change my HUD, which is a problem because this also overrides the setting "automatically replace hotbar 1 with pet hotbar when mounted", makes it very hard to use mount actions, which are essential in the PvP mode Rival Wings, but this happens with all mounts with actions even in the world.

Note this problem was introduced in either patch 4.5 or 4.4, this setting didn't reset by changing HUD layout before this.