Another race condition with coincident holes

[mourner]

#112 introduced a new failing case which was working before:

[
[[4116,-20],[4116,-8],[4096,-8],[4096,223],[3950,223],[3950,685],[3659,685],[3659,800],[3368,800],[3368,916],[3222,916],[3222,1031],[2931,1031],[2931,1147],[2785,1147],[2785,1031],[2640,1031],[2640,1262],[2931,1262],[2931,1378],[2494,1378],[2494,1493],[2348,1493],[2348,1609],[2203,1609],[2203,1839],[2057,1839],[2057,1955],[1911,1955],[1911,2185],[1766,2185],[1766,2532],[1620,2532],[1620,2647],[1475,2647],[1475,2877],[1183,2877],[1183,2993],[1038,2993],[1038,3338],[892,3338],[892,3454],[601,3454],[601,3338],[164,3338],[164,3454],[18,3454],[18,3223],[309,3223],[309,2993],[-20,2993],[-20,916],[18,916],[18,1031],[309,1031],[309,916],[455,916],[455,800],[601,800],[601,570],[746,570],[746,338],[892,338],[892,223],[1038,223],[1038,107],[892,107],[892,-20],[4116,-20]],
[[455,2416],[601,2416],[601,2301],[455,2301],[455,2416]],
[[455,1955],[601,1955],[601,1839],[746,1839],[746,1493],[455,1493],[455,1955]],
[[1766,1839],[1911,1839],[1911,1724],[1766,1724],[1766,1839]],
[[1911,1724],[2057,1724],[2057,1609],[1911,1609],[1911,1724]],
[[746,1493],[892,1493],[892,1378],[746,1378],[746,1493]],
[[2057,1378],[2203,1378],[2203,1262],[2057,1262],[2057,1378]],
[[1766,1147],[1620,1147],[1620,1262],[1911,1262],[1911,1031],[1766,1031],[1766,1147]],
[[746,1262],[892,1262],[892,1147],[746,1147],[746,1262]],
[[1911,107],[1620,107],[1620,570],[1475,570],[1475,685],[1620,685],[1620,800],[1475,800],[1475,916],[1766,916],[1766,570],[2203,570],[2203,107],[2057,107],[2057,-8],[1911,-8],[1911,107]],
[[1911,1031],[2203,1031],[2203,916],[1911,916],[1911,1031]],
[[3077,454],[2931,454],[2931,338],[2640,338],[2640,685],[2348,685],[2348,800],[2203,800],[2203,916],[2640,916],[2640,800],[2931,800],[2931,685],[3222,685],[3222,570],[3368,570],[3368,454],[3513,454],[3513,338],[3077,338],[3077,454]],
[[2203,107],[2348,107],[2348,223],[2494,223],[2494,-8],[2203,-8],[2203,107]]
]

[mourner]

Slightly reduced:

[
[[4116,-20],[4116,-8],[4096,-8],[4096,223],[3950,223],[3950,685],[3659,685],[3659,800],[3368,800],[3368,916],[3222,916],[3222,1031],[2931,1031],[2931,1147],[2785,1147],[2785,1031],[2640,1031],[2640,1262],[2931,1262],[2931,1378],[2494,1378],[2494,1493],[2348,1493],[2348,1609],[2203,1609],[2203,1839],[2057,1839],[2057,1955],[1911,1955],[1911,2185],[1766,2185],[1766,2532],[1620,2532],[1620,2647],[1475,2647],[1475,2877],[1183,2877],[1183,2993],[1038,2993],[1038,3338],[892,3338],[892,3454],[601,3454],[601,3338],[164,3338],[164,3454],[18,3454],[18,3223],[309,3223],[309,2993],[-20,2993],[-20,916],[18,916],[18,1031],[309,1031],[309,916],[455,916],[455,800],[601,800],[601,570],[746,570],[746,338],[892,338],[892,223],[1038,223],[1038,107],[892,107],[892,-20],[4116,-20]],
[[455,1955],[601,1955],[601,1839],[746,1839],[746,1493],[455,1493],[455,1955]],
[[1766,1839],[1911,1839],[1911,1724],[1766,1724],[1766,1839]],
[[1911,1724],[2057,1724],[2057,1609],[1911,1609],[1911,1724]],
[[746,1493],[892,1493],[892,1378],[746,1378],[746,1493]],
[[1911,1031],[2203,1031],[2203,916],[1911,916],[1911,1031]],
[[3077,454],[2931,454],[2931,338],[2640,338],[2640,685],[2348,685],[2348,800],[2203,800],[2203,916],[2640,916],[2640,800],[2931,800],[2931,685],[3222,685],[3222,570],[3368,570],[3368,454],[3513,454],[3513,338],[3077,338],[3077,454]],
]

[mourner]

Reduced more:

[
[[2,12],[2,20],[25,20],[25,12]],
[[7,18],[7,15],[5,15]],
[[19,18],[19,17],[17,17]],
[[19,17],[21,17],[19,16]],
[[7,15],[9,15],[7,13]],
]