Alliance Raid not filling up when finding members

Last few weeks I have been running The Orbonne Monastery where members have left the raid and we've had to refill our ranks. For some reason we're unable to find members to refill despite having friends, FC or LS members waiting in queue. It doesn't seem to really matter which role is in need.

Stranger still is that it seems to only affect one of the three alliances. Example Alliance A, B and C might all be missing members but only Alliance A and B will be able to refill their group.

This most recently occurred this evening:
Date & Time: September 8th , 2:30 am Sever Time
World name: Hyperion/Primal
One alliance had been looking for members since the 2nd boss. We managed to clear but lost more members in the other two alliances. Those two alliances refilled instantly but the one alliance, who had be down since 2nd boss never received members in progress.


Date & Time: Past month
Frequency: When ever multiple parties lost members
World name: Hyperion/Primal

Party or solo: Alliance Raid
Area and coordinates: Orbonne Monastery

Same experience this evening.

A few players dropped out of duty as soon as they saw that it was The Orbonne Monastery. Alliance B was recruiting players since the duty commenced.

Date & Time: September 9th , 1:30 am Sever Time
World name: Hyperion/Primal

Here's a screenshot where a player is mentioning that they have someone waiting to join in-prog but they aren't getting a queue pop.
https://i.imgur.com/bvsvGcf.jpg

" he's in queue, idk why it's taking so long with a dps slot open"