Nice bug :-)

(Don't have time to look into this now)

benchmarks/bugs/bug-extrude.geo

+lc = 1;
+lc2 = 0.5; // for the pegs
+
+Point(77)={17.7000,0,0,lc};
+Point(78)={17.5325,0.8419,0,lc};
+Point(79)={17.0556,1.5556,0,lc};
+Point(80)={16.3419,2.0325,0,lc};
+Point(81)={15.5000,2.2000,0,lc};
+Point(82)={14.6581,2.0325,0,lc};
+Point(83)={13.9444,1.5556,0,lc};
+Point(84)={13.4675,0.8419,0,lc};
+Point(85)={13.3000,0.0000,0,lc};
+Point(86)={13.4675,-0.8419,0,lc};
+Point(87)={13.9444,-1.5556,0,lc};
+Point(88)={14.6581,-2.0325,0,lc};
+Point(89)={15.5000,-2.2000,0,lc};
+Point(90)={16.3419,-2.0325,0,lc};
+Point(91)={17.0556,-1.5556,0,lc};
+Point(92)={17.5325,-0.8419,0,lc};
+CatmullRom(30) = {85,84,83,82,81,80,79,78,77};
+CatmullRom(31) = {85,86,87,88,89,90,91,92,77};
+
+Point(97)={46.9,1.5,-.7814,lc2};
+Point(98)={46.7536,1.8536,-.756,lc2};
+Point(99)={46.4,2,-.6946,lc2};
+Point(100)={46.0464,1.8536,-.6332,lc2};
+Point(101)={45.9,1.5,-.6078,lc2};
+Point(102)={46.0464,1.1464,-.6332,lc2};
+Point(103)={46.4,1,-.6946,lc2};
+Point(104)={46.7536,1.1464,-.756,lc2};
+Point(105)={46.9,-1.5,-.7814,lc2};
+Point(106)={46.7536,-1.8536,-.756,lc2};
+Point(107)={46.4,-2,-.6946,lc2};
+Point(108)={46.0464,-1.8536,-.6332,lc2};
+Point(109)={45.9,-1.5,-.6078,lc2};
+Point(110)={46.0464,-1.1464,-.6332,lc2};
+Point(111)={46.4,-1,-.6946,lc2};
+Point(112)={46.7536,-1.1464,-.756,lc2};
+Point(113)={51.1,-1.5,-1.5107,lc2};
+Point(114)={50.9536,-1.8536,-1.4853,lc2};
+Point(115)={50.6,-2,-1.4239,lc2};
+Point(116)={50.2464,-1.8536,-1.3625,lc2};
+Point(117)={50.1,-1.5,-1.3371,lc2};
+Point(118)={50.2464,-1.1464,-1.3625,lc2};
+Point(119)={50.6,-1,-1.4239,lc2};
+Point(120)={50.9536,-1.1464,-1.4853,lc2};
+Point(121)={51.1,1.5,-1.5107,lc2};
+Point(122)={50.9536,1.8536,-1.4853,lc2};
+Point(123)={50.6,2,-1.4239,lc2};
+Point(124)={50.2464,1.8536,-1.3625,lc2};
+Point(125)={50.1,1.5,-1.3371,lc2};
+Point(126)={50.2464,1.1464,-1.3625,lc2};
+Point(127)={50.6,1,-1.4239,lc2};
+Point(128)={50.9536,1.1464,-1.4853,lc2};
+CatmullRom(38) = {101,100,99,98,97};
+CatmullRom(39) = {101,102,103,104,97};
+CatmullRom(40) = {125,124,123,122,121};
+CatmullRom(41) = {125,126,127,128,121};
+CatmullRom(42) = {109,110,111,112,105};
+CatmullRom(43) = {109,108,107,106,105};
+CatmullRom(44) = {117,118,119,120,113};
+CatmullRom(45) = {117,116,115,114,113};
+
+Line Loop(46) = {-31,30};
+Plane Surface(47) = {46};
+Line Loop(48) = {-38,39};
+Plane Surface(49) = {48};
+Line Loop(50) = {-43,42};
+Plane Surface(51) = {50};
+Line Loop(52) = {-40,41};
+Plane Surface(53) = {52};
+Line Loop(54) = {-45,44};
+Plane Surface(55) = {54};
+
+// extruding this makes Gmsh go nuts
+Extrude Surface {51, {0,0,3}};