Merge lines in direction error about lftools HOT 4 OPEN

"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.

from lftools.

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?

from lftools.

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

from lftools.

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

from lftools.