Yes I check often for a new version from the hub, install it & had just done so shortly before she turned 98.
This time when it happened she only had 4 quests in her log, we had a better idea of what the sticky quest might be, & we attempted to enable the quest module in between each completed quest, as well as reloads, restarts & reboots.
Darkmoon Faire -Strength quest collecting Grisly trophies was completed but she couldn't turn it till next month, so she dumped it, nothing.
Scallion Quest from Halfhill in Pandaria, nix.
Ran the opening Legion content & acquired first Artifact weapon, class Hall etc, nada.
Then she went back to Draenor to complete the only quest left.
Rite of the Talon Priests -Spires of Arak is her favorite quest chain in Draenor, & normally she would have had it completed before leaving Draenor, but both of these toons were leveled quickly while she established herself on a new server & she was given the quest almost at the same time she dinged 98 which triggers the Legion Quest.
On her original toon with this issue she hadn't been able to use Carbonite Quest Module from 100 till she opened up WQ at 110. The opening Legion quest at 98 auto accepted into her log but she wanted to wait till 100 before starting... we are pretty sure she was in the Spires of Arak & had been doing the Talon Priests quest line at the time her game locked up but that got lost in the snarl somewhere, neither of us remembered that & she had abandoned a bunch of quests trying to fix it... either not enough or she had re-accepted that particular quest before checking again to see if the Carbonite Quest Module would work yet
At 110 she went back to Draenor to complete a few things, finished off the Spires content, turned in an old Darkmoon Faire grisly trophy quest & abandoned another couple of old quests... tried the Quest Module again & voila!
I will be leveling a new toon through Draenor in the next couple weeks (middle of house remodel) & I'm planning on picking up the Rite of the Talon Priests quest in the Spires of Arak before I get the quest for Legion & if it locks up, abandon just that quest to see if I can recreate the issue.
I'll post back here & let you know.