Open your model with War3 Model Editor.
Windows > Node Manager
Right click the helper Bone_Root (The top node with a exclamation balloon icon).
Click "Edit Node" or press N.
Click the Scaling button (it is under the Rotation button).
Below, there are two drop-downs, the left one is Global Sequence ID and the right one is the Interpolation type, click the latter then select "None".
Delete
1000: { 1, 1, 1 }
1500: { 1, 1, 1 }
2000: { 1, 1, 1 }
if you want the filesize to be decreased a little bit.