We have discovered that using 4.26, something has changed that is breaking the export of a skeleton Mesh that is imported into Blender. The Mesh is deformed and this works fine using Unreal 4.25. Note, this was tested using the 2016 compatibility option during export for both versions and all other options used the defaults from unreal.
Also forgot to mention, the skeleton mesh this issue was discovered, is the ALS v4 BP on the Market (Free) and exporting the AnimMan. With 4.26, tried very compatibility option and none of them worked.
You did not have this issue using 4.26 of unreal and exporting to blender?