That bug got introduced in v1.28.2.76/v1.30.0.5 with "Backported from LL's viewer fixes to excessive octree recalculations for meshes. Fixed a bug in that fix that was causing an issue when sitting on scripted objects changing the camera view, with those objects vanishing from view". Sadly my "fix" (and the "better fix" by LL adopted in v1.28.2.77/v1.30.0.6) was not good enough...
I reverted this code change and will publish fixed releases today...