Seems highly non logical to me.

UWhy just for some features? Is there some LIFO going on?

Lastvertex IN Firstvertex Out?

R you sure no other issues are present?

hh

You can compare direction prior to merging whith post merging using a Orientationextractor.

The orientation of Supplier lines may be reversed when you checked the Process Duplicate Supplier and also set "Build Polygons" to the Geometry Merge Type parameter. I guess that FME would prepare to build a polygon with Left Hand rule from some Supplier lines.

Do you really need to collect some Supplier lines and build polygon from them for each Requestor?

If not, consider swapping Requestor and Supplier inputs and setting "Attributes Only" to the Feature Merge Type parameter.

Thank Takashi, I had a number of requester features that needed the same line geometries so I ended up swapping the Requestor and Supplier inputs and creating a many-to-one join from the list attributes.

I was just curious as to why line geometries would be getting flipped through the supplier.

​I'm having the same issue with the change of orientation. I have a data table feature as the requestor and geometry as the supplier, I need all the duplicate geometries with original orientation.  I have to check start and/or end coordinates against the original coordinate(s) then use Orientator transformer to reverse back to original orientation.