"The gym is under attack" cooldown bug/workaround?

Ok, so we all know that within 10 minutes of a defending pokemon being kicked out from a full gym, you can't add a new one.

I've fought plenty of gyms but I witnessed something today I've never seen before when I was taking down a half-fought gym (the previous attacker appears to have given up and it later dawned on me why).

So I was kicking out the mons (with depleted motivation) and when I came to the last one, a Chansey, a Blissey was added. I was taken aback and thought perhaps something happened in the last 10 minutes before I started such that the "rule" didn't apply.

So I left the gym and walked around to catch pokemon. The gym filled up almost immediately (this group of Mystic players in my neighbourhood have each others' accounts :eyeroll:).

I noted that I left the gym at 8.57pm and returned at 9.18pm. I start again, taking down the Chansey and the newly added Blissey, Snorlax, Flareon without any resistance (ie. berry feeding). When I come to the last two (Dragonite and Machamp), a new Blissey was added. Deja vu.

I didn't know what was happening but thought I'd be a fool to start Round 3 and waste potions if there was some sort of new trick. I went off to do something else and minutes later, from the distance, I saw the gym being attacked again but it remained blue with a slightly different roster of pokemons. The Dragonite and Machamp that were there when I gave up were gone but the Blissey was there with other new pokemons. The next attacker probably had the same experience I did.

On my part, I'm absolutely certain I took less than 10 minutes to knock out the first four pokemons. I was baffled and at the same time understood why the attacker before me gave up. I've never seen anything like this and it annoyed me more than that network error we used to get when we attack a gym raided earlier that day.

Has anyone else experienced anything similar recently? Is this a bug with the new update, did the 10-minute cooldown get amended with the update or is there a new cheat/workaround to circumvent the 10-minute cooldown?