The alpha 9.1e on forge 12 2796 has a weird bug where the tree becomes a graphical only entity without clipping and moves to the left and forwards about a block for 200 ticks or so.

This only happens if tree falling is turned off.

Not sure how to describe it. The tree just kind of teleports 2 blocks forwards and to the left, and then POPS into logs.

This seems to have happened near the time you added the optional tags in one of the latest git builds. A self compiled build from 12/9 doesn't have this, but also doesn't have a few bug fixes added since then. I'm not sure when the bug started showing up, as I'd only compiled a version on the 9th and on the 19th, and the issue was present on the 19th.