Admin actions don’t present themselves in that way and they would have deleted your bases in entirety, not just doors and placeables. It would show as lost stability. So we can rule that out.

Decay is currently 10 days. Check the server settings to see if this is the case. Some servers are not in line with the majority. An example is an NA PvP server I visited recently that is 1x XP and harvest rates which is an anomaly compared to the rest at x4.

Did you increase the proximity as I suggested?

If you have done both then it is either a bug that they disappeared or your things decayed and someone dismantled them.