Sergei

@Komzpa please take a look too.

@pramsey please consider re-opening the issue as second case haven't been fixed and I am working on it currently. I'm currently investigating the second case. Here's a simplified case that...

Reproducing in PostGIS: ``` # SELECT ST_ReducePrecision('SRID=3857; POLYGON((2027603.4369208599 8183234.881054974, 2027112.7433669677 8183234.881054974, 2027112.7433669677 8183529.661146606, 2027603.4369208599 8183529.661146606, 2027603.4369208599 8183234.881054974 ),( 2027343.8203659565 8183290.493334692, 2027335.5549540422 8183271.617113829, 2027338.5549540422 8183271.617113829, 2027340.0243713208 8183271.314402774, 2027339.723808695 8183273.065802623, 2027340.8926633487 8183267.6602488635,...

Case 2 does not depend on exact numbers and is easy to reproduce with following conditions: * overall similar geometry, of course, rectangle with a hole near it's lower edge...

Yes, this is a robustness issue. I made a diagram showing layout of vertices in `BufferBuilder::edgeList` at this line: https://github.com/libgeos/geos/blob/4526237dfadd47eb4fc2f54a3578d45e6d63b9d9/src/operation/buffer/BufferBuilder.cpp#L429 Labels are edge index / point index in edge, image...

No problem, I should have found that commit myself and just ask in Discord or create an issue. Maybe it is related to SPOT code?