Thavnairian Onion not working correctly

Time: August 30 3:47 PM PST
Frequency: 1
World name: Excalibur
Character name: Sol Aureus
NPC name: Hank
Monster name: N/A
Class/Level: N/A
Party or solo: N/A
In-game time: N/A
Area and coordinates: N/A
Steps:
1. Selected Hank in the Chocobo Stables interface (Hank is a chocobo owned by another player and was capped at rank 10 at the time of the bug).
2. Selected "Yes" at the "Further training will not result in additional EXP. Continue trainin?" prompt.
3. Selected a Thavnairian Onion as the training reward.
4. Hank consumed the Thavnairian Onion, no EXP was awarded and Hank's rank cap was not increased.

NOTE: Before this bug occurred, I fed my own chocobo, Fortune, a Thavnairian Onion. Every single menu option, prompt, and warning was the exact same (Select chocobo stables → Tend to a Specified Chocobo → [Select Chocobo] → "Further Training will not result in additional EXP. Continue Training?" prompt appears → Select "Yes" → Training Cutscene plays → Fortune gained EXP and his rank cap was raised. Hank did not gain EXP and his rank cap was not increased.) I would also like to note that Hank was indeed capped at rank 10 with an orange rank number which indicates that he was capped and ready for a Thavnairian onion.

NOTE2: If this mechanic is working correctly, then I believe there is a missing prompt or warning to the player to indicate that they cannot increase the rank cap of other player's chocobos, because as it currently stands there is absolutely no indication to the player whatsoever that this is the case.