17. did you remove all old tar and salt spots or just the locations sark reported in the original post?
in case you didnt remove others, there was a huge tarspot poping up by loading issues long time ago on the top of the mountain south of misery island. it should be around the middle of zone 779, there is only one huge mountain. if you need the exact cords i am sure sark can post them since he live close and know this tarspot as well.
9. buildings do glitch when they are sunken to the ground and the top reach the same level than dirt surface. they also can completly dissapear in certain angels. to reproduce it please check scrapper freeway walls zone 978 pos 630/530 on the peaceserver
there are glitches if buildings overlap into each other, for example roofs connected to each other ( with the new arch system as well )
these could be the problem the player who reported had, i can not confirm glitching floors unless they are sunken into the ground.