Reopening with the proper format since my previous entry was moved to insufficient information.

Time: June 11th, around 17:00 EST
Frequency: Once (though I assume it always happens; due to the nature of PvP, I have not had the opportunity to reproduce it)
World name: Brynhildr (Primal datacenter frontlines)
Character name: Thekk Everdream
Retainer name: None
NPC name: None
Monster name: None
Class/Level: Astrologian/60
Party or solo: Alliance, 72 players
Area and coordinates: The Fields of Glory (Shatter) - 17.6, 19.0 (Northwestern outpost)
Steps:
1. Maelstrom took control of the outpost
2. Adders and Flames came to the outpost and killed all Maelstrom members in the area
3. Adders and Flames entered the outpost area in order to capture
4. Since both Adders and Flames had around the same number of players, control progress did not change and Maelstrom kept control of the outpost. Given that there were no Maelstrom members in the area, the outpost should have became unoccupied.
5. Adders won the fight against Flames and took control of the outpost once sufficient enemies were taken care of, but only then did control progress start changing.

I do not believe my connection and system information is relevant to the bug since it is purely gameplay related. As such, I will omit it.