Trouble with the BRepAlgo_Fuse Methode

Hello, i have a little troubles with the aforementioned Method, i have a list of faces that i want to fuse together without a seam (hence the usage of the older method).

However, the list of faces may contain same faces twice with different ids, so it would be troublesome to check for duplicates.

I start by fusing two faces, then i add the others one by one with the fuse method witch works fine, but whenever a face is added that was added before, i get

Traceback (most recent call last):
  File "<interactive input>", line 1, in <module>
  File "C:\Users...lib\site-packages\OCC\BRepAlgo.py", line 2885, in __init__
    _BRepAlgo.BRepAlgo_Fuse_swiginit(self, _BRepAlgo.new_BRepAlgo_Fuse(*args))
RuntimeError: Standard_ConstructionError
Geom_TrimmedCurve::U1 == U2

Which i don't understand, i can easily fuse the same shape to itself, so why would this cause trouble..

Does anyone have any idea as to why this should be?

Any help is much appreciated!