Hunter Pet Health at take off (I have flying): 162K Health. Hunter Pet Health on landing 140K Health. Repeatable on demand bug.
Edit: Tried different pets. All pets affected. Warlock Pets are ok. Tried a different Hunter. Same results with the pets.
IIR, this was a bug back in 8.1 or 8.15 that was eventually patched.
Does this still only apply to beast mastery hunters? I have a vague recollection that it had to do with how beast mastery calculated stamina/HP for a freshly summoned pet or something.
Does it on BOTH MM and BM.
This was an issue back at the start of BfA. Also, ONCE AGAIN, the tank pets are EXTREMELY fragile. I use Spirit Beasts (Arcturis) that poor bear is getting his bear hiney spanked.
I am seeing this too - BM hunter. I take off with my pet at 100% health - I land, and it comes back with 92% and then if I give it a second, it goes DOWN 5% more (to 87%) before health regen kicks in and it starts to go up. Subsequent takeoffs and landings back to back result in even more health lost on my pet. Presumably, with enough time, I could kill my pet just from mounting and dismounting over and over. Dismissing it and summoning it back also results in a loss of health on the first summon, but doing it back to back doesn’t take it any lower than the first summon did.
Please fix this issue, everytime I dismount off of a flying mount my pet’s health goes from 100% to around 40%. I think enough people have been complaining and having this same issue that I would imagine it should get addressed already
I too have experienced this over site and it’s still happening today. What I did notice is possibly why. This might have been happening since 7.3.5 when Blizzard introduced the zone scaling system. I use older exotic rare pets mostly from WotLK and earlier. My guess of a conclusion is when the pet spawns, whether you change pets or dismount from flight. For a second I believe it’s spawned at the original or maxed scale level from their original zone before you tamed them. Then after being spawned the pet scales back to your level, assuming your max level now. I believe at this time to avoid this until one day Blizzard addresses this over site is to tame a pet from a higher expansion pack with a higher level with the same or similar abilities. I know it’s not the same look that most players are looking for, but maybe for competitive guilds/players doing dungeons and mythic + raids/PvP this will not leave them handicapped all the time. If it’s for show all there is to do what I do and hit the heal pet button. This is just a theory.
It’s also happening when you level. I have a lowbie hunter level 2x and it does the same thing when I level. IT’s been reported for months and Blizzard does nothing about it. Good luck! I’ve unsubbed due to multiple bug that affect gameplay and hasn’t been fixed in 6+ months. Blizzard shows they care…
This is a very annoying bug and still very much there.
Been happening for years. Apparently, Blizzard doesn’t care about this issue. Not a response from anyone. Of course, the in-game ticket system is a joke. Not that they would respond anyways. 
5+ months later and Blizz still doesn’t care 
Bug still exists.
I use a spirit beast and it’s an excuse to toss him the overstocked meat that’s sitting in my bank to get him back to 100%, but this would surely be an extreme annoyance for anyone that prefers a herbivore pet.
Not fixed yet
Still happens to ALL allied race hunter pets.
Additionally, all allied race hunter pets take an EXTREME amount of damage in combat compared to the regular races’ pets. This has been incredibly frustrating when leveling allied race hunters.
This is an issue specifically with Tenacity pets, as far as I can tell. When they spawn, they lack the Tenacity HP buff, and when that buff applies to them a few seconds later, unlike players, they do not retain 100% HP, instead retaining the same absolute HP they had before, and thus ending up with sub-100% HP. However, when you take off and land, they retain the same percentage HP they had when they despawned from taking off (and thus less absolute HP. If you repeat this over and over, the pet’s current HP keeps going lower and lower.
My pet has the same issue and its very frustrating when dismounting and have to fight.