If I’m not mistaken, is defaultMaterial the Motor6D attached to the handle? If so, are you also using a script that turns the welding of the tool into a Motor6D? If so, I think you should instead name defaultMaterial to Handle instead and export that animation.
If you aren’t using the script, it actually helps with animating the tool’s handle. Normally, you cannot animate the handle of a tool. Because, it’s going to turn into a weld that welds onto the player’s arm; Therefore, any animation regarding to the handle will not animate. But the owner of the script (who’s actually the owner of Moon Animator 2) created a script specifically for that reason, to animate the handles! Just put in “Tool Motor6D” and find the name “xSixx” (or somewhere in that lines) as the owner of the script.
Or, alternatively, you could follow this tutorial whom also created the same thing.