Silverpine Forest is Unplayable with Replay Quests

Quest: Rise, Forsaken
Variable: Beat the zone once, come back with Party Sync activated
Issue: Agatha will never spawn, making the quest impossible and progress in Silverpine stuck indefinitely
Suspected bug: Agatha’s NPC flag to spawn during this quest is incompatible with the Replay function
Current workaround: You must be in a party with someone who has NOT completed Rise, Forsaken on that character. Agatha will spawn without issue for the first-time completion.

Since Party Sync works from literally anywhere in the world, I like DPS queueing with my lower-leveled partner while he alt-tabs and plays something else.
During wait times, I’ll often take my higher level character via Party Sync to replay older questing zones. Silverpine in particular is an easily accessible favorite of mine.

Progress is impossible unless you have someone with you for Agatha to spawn. I’ve tried everything Wowhead suggests, from being dismounted the whole run, dismounted on quest pickup, and trying to spawn her at the gate of Fenris Isle’s keep.
The only thing that works is having a partner, on that specific quest, in your party and in Silverpine, who has never done it on that character before.