It usually means that one of your bone has a scale on it. Please check if it's the case.

Here is the mel script to make sure no scale is applied on any bone:

string $joints[] = `ls -type "joint" -long`;
print $joints[0]; //the first joint
* loop through all objects */
string $joint;
for ( $joint in $joints ) {
setAttr ($joint + ".scaleX") 1;
setAttr ($joint + ".scaleY") 1;
setAttr ($joint + ".scaleZ") 1;

To be able to create Apex files, you will need to install the Nvidia Physx DCC plugin. The plugin for various Maya versions can be found here and is now maintained by Golaem. Please get in touch with our support if your Maya version is not listed here. Notice that within Linux, you may have various errors when the plugin is loaded / unloaded in Maya: this is expected and does not have any impact on the cloth configuration.