The first one, the "immortal" enemy that has been reported through most of ToME development and obviously can still happen :

This one was very annoying, as while that ooze is visible i was prevented to dig, very fortunately i had a lantern in stock that i forgot to transmogrify and had very little light radius, so i was able to dig .
Very annoying as if the thing had been near the stairs, i wouldn't have been able to dig at all and the ruined dungeon would have become unexplorable.
Now the 2nd bug, more problematic this one as i couldn't find a workaround : one of the random bosses (the ones you need to kill in order to be able to use all the orbs in the last door on the north of the map) wasn't there

I dug and explored the whole area for a long time in case it was some annoying random teleporter boss, but despite going everywhere i could, nothing.
Very annoying as it cuts the access to the final door due to one of the Orb that will stay inactive.
I attach the part of the log that correspond to my whole Ruined Dungeon exploration in case it helps