The reason of this issue is in incorrectly interpreted the generic class "TheExtPC" (eliminated after the fix 0024773) as Extrema_ExtPC2d. Correct interpretation must be "Extrema_EPCOfExtPC2d" class.
Now this problem has been fixed in the class Geom2dGcc_Circ2dTanCenGeo.
New testgrid "lowalgos 2dgcc" has been created.