Merge lines in direction error

[AlisterH]

Merge lines in direction produces this rather incomprehensible error if there is a line that starts and ends at the same point:

Calculating feature informations...
Merging lines...
Saving output...
Traceback (most recent call last):
File "C:\Users/alister/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\lftools\processing_provider\Vect_DirectionalMerge.py", line 334, in processAlgorithm
fet.setGeometry(QgsGeometry.fromPolylineXY(item[0]))
TypeError: index 0 has type 'float' but 'QgsPointXY' is expected

Execution failed after 0.01 seconds

[AlisterH]

"Lines to Polygon" also produces an error if there is a line that starts and ends at the same point.
I note that the "native" (built in) QGIS "lines to polygons" algorithm doesn't error in this case.

[LEOXINGU]

I fixed "Lines to Polygon" tool, but I didn't find the problem with "Merge lines in direction". Could you send some example as shapefile or geopackage?

[AlisterH]

Ah, yes, it seems it doesn't error with every "line that starts and ends at the same point". But here is an example.
example9.zip

[AlisterH]

I note also that it generally doesn't join lines which would form (or already are) a feature with two vertexes at the same point (except if it is the start and end points). Here is a file to demonstrate.
example2.zip