The Underpin Despawning

Hi,
I am getting “The Underpin” despawn on me during delves, this has happened 5 or 6 times now. I am always still at full to near full health, I am not out of range or line of sight, but he will get to about 50% health & then despawn. When he doesn’t despawn I get a kill credit, which is nice for the achievement & all the appropriate drops etc… but on despawns he doesn’t drop the map for the extra loot, no credit, no upgraded items, no gilded crests etc at the end of the delve…
This time in "The Spiral Weave’ he just turned, ran off & despawned & all he left was ‘Pacifists Rig’ & ‘Underscout’s Cap of the Fireflash’ & nothing else, both of those are useless for me & didn’t even get a kill credit. I am loosing 2000 Undercoins each time I have to buy a wavescrambler 2000 to spawn him as well as the scrambler itself, PLUS all the Bonus loot etc for doing a complete clear on a bountiful delve.
Then, after the Underpin situation & before I killed the final boss it still said I have 1 main mob walking around the delve. I checked the whole delve before I killed the final boss & it was completely empty so I had killed everything. I then went back, killed the boss & it still says there is 1 mob remaining despite the place being completely empty, so as well as everything else I didn’t get, I also lost out on the fully Upgraded Nemesis Strongbox loot.!! Plus all that, Brann looses out on Loads of XP!!
I have reported this through a ticket, & then “Game Master Adutaggixu”, eventually came back & stated “We have received several reports of this issue and are investigating it. and I’m afraid taht Customer Support does not have a workaround or resolution that can be provided.”. They can look at the game log & what I am saying… even if they had just sent me the “Wavescrambler 2000” &/or “2000 Undercoin”, at least I wouldn’t be on a negative & have the ability to do it again. As of now I don’t have enough coins to retry… & in total have now lost 10,000 - 12,000 undercoins because of this bug.