Property of path which making it not visible in rendering software?

[AvivEsh]

I have a pdf which contains the following path:

'items': [('re', Rect(380.8199768066406, 341.70001220703125, 381.239990234375, 354.4800109863281), -1), ('l', Point(381.239990234375, 354.4800109863281), Point(368.4599914550781, 341.70001220703125))], 'type': 's', 'stroke_opacity': 1.0, 'color': (0.0, 0.0, 0.0), 'width': 0.36000001430511475, 'lineCap': (1, 1, 1), 'lineJoin': 1.0, 'closePath': False, 'dashes': '[] 0', 'rect': Rect(368.4599914550781, 341.70001220703125, 381.239990234375, 354.4800109863281), 'layer': '', 'seqno': 8279, 'fill': None, 'fill_opacity': None, 'even_odd': None

I cannot see the diagonal line in any apps like acrobat reader and others.

But for example in another file, I have this path

'items': [('l', Point(381.239990234375, 354.4800109863281), Point(368.4599914550781, 341.70001220703125))], 'type': 's', 'stroke_opacity': 1.0, 'color': (0.0, 0.0, 0.0), 'width': 0.36000001430511475, 'lineCap': (1, 1, 1), 'lineJoin': 1.0, 'closePath': False, 'dashes': '[] 0', 'rect': Rect(368.4599914550781, 341.70001220703125, 381.239990234375, 354.4800109863281), 'layer': '', 'seqno': 474, 'fill': None, 'fill_opacity': None, 'even_odd': None}

which is visible.

Maybe there is a property that is checked in one and not the other? I am clueless

[JorjMcKie]

This is a post for "Discussions" not an issue.
Transferring ...

Please always provide the example file (preferably small, or just the page). How could we ever conclude something by staring at code alone?