Yes I am finding the same sort of random placeable decay and despawn issues. (On the same server as OP.)
This past week I logged into find:
A) Large carpet in middle of a room placed on ceiling tiles had decayed and despawned … causing two items that were placed on it to lose stability and despawn
B) a tier 3 Derkato shrine on black ice foundations on a base with a 168 hour timer which I had logged out on 48 hours earlier had gone into decay and despawned the day before. Also causing the despawn of Jade cat statues that were placed on it. And of course loss of items in the shrine including an Arch-priest.
C) a tier 3 Yog pit decayed and despawned … again in a 168 hour timer base that was not in decay. I think I visited it four days prior. Again it’s despawn caused a drum that was placed on it to despawn.
I have several other items saying they are decayed and will be abandoned in the future or the past. I had made a detailed bug report of this issue but it’s been auto-closed: