I'm pretty sure something is wrong with the server setup.

Flawless defeat is when you lose without any of the opposing team dying in arena mode. Likewise flawless victory is when you win without taking a single casualty.

My guess is that the conditions for this is if everyone is alive on map end, and so on a non-arena map this happens regularly. The server must think you're playing arena and so is playing this sound.

Below are all the items classes can use to self-heal. Every single class has some sort of self-healing.

Scout

• Mad Milk
  • returns 60% of damage done to soaked enemies as healing for self and allies
• Candy Cane
  • If the scout kills an enemy (even without the Candy Cane, as long as the Candy Cane is equipped) the enemy's body drops a small health kit

Soldier

• Concheror
  • on use, returns 35% of damage done as healing for self and allies within a radius
• Black Box
  • each successful hit yields +15 hp per enemy hit
• Half-Zatoichi
  • upon kill, heals 50% of the killed enemy's max hp (and can overheal).
    (Note that if holstered/switched away without a kill, 50 health will be deducted from the player's current health. If the player is below 50 health points, the weapon can not be holstered until the player gets a kill or they get more health).

Pyro

• Phlogstinator
  • upon full "Mmph!", taunting grants full hp, damage resistance, and guaranteed critical hits
• Powerjack
  • restores +75 hp with kill

Demoman

• Persian Persuader
  • any ammo picked up from boxes or weapons is converted into health
  • dispensers provide no ammo, but resupply cabinets still do
• Eyelander/Nessie's Nine Iron/Horseless Headless Horsemann's Headtaker
  • each successful kill increases speed by 8%, max hp by 15, and heals for 15
• Half-Zatoichi
  • upon kill, heals 50% of the killed enemy's max hp (and can overheal).
    (Note that if holstered/switched away without a kill, 50 health will be deducted from the player's current health. If the player is below 50 health points, the weapon can not be holstered until the player gets a kill or they get more health).

Heavy

• Sandvich
  • heals +300 hp over 4 seconds.
• Dalokohs Bar/Fishcake
  • heals and increases max hp by 50 for 30 seconds

Engineer

• Dispensers
  • Level 1: +10 hp per second
  • Level 2: +15 hp per second
  • Level 3: +20 hp per second

Medic

• Automatically heals +3 hp per second
• Blutsauger
  • heals +3 hp every successful hit, but drains -2 hp per second
• Kritzkrieg
  • Oktoberfest taunt heals self +11 hp
• Quick Fix
  • while using ÜberCharge, heals patient and medic +100.8 hp per second or +302.4 hp per second if out of combat
• Amputator
  • while taunting, heals all allies at +25 hp per second (or +75 hp per second if out of combat) within a certain radius for 4.2 seconds

Sniper

• The Cozy Camper
  • heals +2 hp per 2 seconds

Spy

• Conniver's Kunai
  • upon backstab, steals all hp from enemy

Misc

• Payload Objectives (Carts)
  • heals +10 hp per second
• Resupply Locker
  • instant full heal
• Health kits
  • small: heals 20.5% of max hp
  • medium: heals 50% of max hp
  • large: heals 100% of max hp