Regular disconnects from Harbinger map + corrupted gem bug

I play a Spectral summoner and have found that using both Spectres and Zombies together will cause the game to crash on maps - about 40% of the time.

However, recently, when playing (with only Spectres to limit crashes) on the Harbinger Beach Map there is a regular game crash, which I assume is the map server, as I am sent to the desktop and when I log back in, all map portals have disappeared.

This has happened 4 times where it was the Beachhead map (about 25% of the time) once with another persons map (which makes about 33% of the time).

It does occur on other maps, but not with the same frequency and as the other maps are not linked to a challenge - not with the same annoyance factor.

As an aside on a different bug, I corrupted a level 20 Raise Zombie gem, it went to level 19 (not unexpected) and then levelled to 20 again.