Extremely peculiar bug: I have a specific rigged mesh object with PBR materials in alpha masked mode (a left thigh piece of a boot) which will disable system avatars' right hands from rendering while it's on screen and worn. This affects both the wearer and any other avatar with a system body visible on screen at the same time as the rigged mesh piece. If the rigged-piece wearer is removed from camera, the hand reappears. If the boot piece has no PBR materials, right hands don't disappear, and if it's not worn i.e. being rigged, also has no effect. If the material is changed from alpha masking mode to opaque or blended, the hand stays visible. An object using the BOM BAKED_UPPER texture the hand texture comes from does not disappear or get a hand-shaped hole in it. Curiously, the matching right thigh piece has no vanishing effect despite using an identical material regardless of alpha mode. Reproduces on SL Viewer 7.1.10 DeltaFPS and Firestorm release 7.1.9, Alchemy beta 7.1.9 and Cool VL Viewer 1.32.2. Turning PBR rendering off in Cool VL Viewer will, as expected, restore the hand, so it is an issue with the PBR shaders. Excuse the ghastly look of my test avatar in a system body, the images attached show the hand being there without the bug-triggering object attached, and immediately being gone with the object attached. I did not create this object myself but luckily it is full perm, so I can share a copy for anyone willing to investigate the bug.