I have done extensive tests with DSBs on an official server and I can say there are two things at play.
One is there is a visual attachment that makes them seem to be properly aligned with the two surfaces, yet when inspected closely you will discover the beam is not actually touching one of the surfaces. Usually the horizontal.
The other is there is a bona fide support issue at play. If an object can be supported prior to server reboot, it should not despawn or deconstruct after reboot. I have seen this so many times over the last week, in unrepeatable, somewhat random fashion. Ceiling tiles that are allowed placement by DSBs will despawn on server restart. This was present during my last testlive deep dive; if this patch corrects it I’ll update my info in a new post here. 