This should be a reproducable example in Python 3.7, Shapely 2.0.2:

import shapely line = shapely.linestrings([ [ 8.985738, 60.712983 ], [ 8.985523, 60.712769 ], [ 8.985278, 60.712175 ], [ 8.985441, 60.711763 ], [ 8.985674, 60.711554 ], [ 8.986364, 60.711158 ], [ 8.986783, 60.71076 ], [ 8.986913, 60.710638 ], [ 8.987753, 60.710386 ], [ 8.987975, 60.710381 ], [ 8.98801, 60.710381 ], [ 8.988991, 60.709666 ], [ 8.989304, 60.709225 ], [ 8.988991, 60.709666 ], [ 8.98801, 60.710381 ], [ 8.987753, 60.710386 ], [ 8.986913, 60.710638 ], [ 8.986364, 60.711158 ], [ 8.985674, 60.711554 ], [ 8.985427, 60.711546 ], [ 8.985205, 60.711582 ], [ 8.985061, 60.711618 ], [ 8.984823, 60.711663 ], [ 8.984621, 60.711681 ], [ 8.984332, 60.711681 ], [ 8.98412, 60.71166 ], [ 8.983526, 60.711579 ], [ 8.982879, 60.711582 ] ]) circle = shapely.polygons([ [ 8.993146, 60.708983 ], [ 8.993075, 60.708632 ], [ 8.992866, 60.708294 ], [ 8.992526, 60.707983 ], [ 8.992069, 60.707711 ], [ 8.991512, 60.707487 ], [ 8.990876, 60.707321 ], [ 8.990187, 60.707219 ], [ 8.989469, 60.707184 ], [ 8.988752, 60.707219 ], [ 8.988063, 60.707321 ], [ 8.987427, 60.707487 ], [ 8.98687, 60.707711 ], [ 8.986413, 60.707983 ], [ 8.986073, 60.708294 ], [ 8.985864, 60.708632 ], [ 8.985793, 60.708983 ], [ 8.985864, 60.709334 ], [ 8.986073, 60.709671 ], [ 8.986413, 60.709982 ], [ 8.98687, 60.710255 ], [ 8.987427, 60.710478 ], [ 8.988062, 60.710644 ], [ 8.988752, 60.710747 ], [ 8.989469, 60.710781 ], [ 8.990187, 60.710747 ], [ 8.990876, 60.710644 ], [ 8.991512, 60.710478 ], [ 8.992069, 60.710255 ], [ 8.992526, 60.709982 ], [ 8.992866, 60.709671 ], [ 8.993075, 60.709334 ], [ 8.993146, 60.708983 ] ]) intersection = shapely.intersection(line, circle) 

The original LineString contains duplicate points, since it is a GPS track going back and forth the same way: The black circle intersects with the blue line (GPS track). The red line is the result. These are the sub Lines of the intersection separated a bit to visualize it better:

The original LineString contains duplicate points, since it is a GPS track going back and forth the same way: The black circle intersects with the blue line (GPS track). The red line is the result. 

These are the sub Lines of the intersection separated a bit to visualize it better:

Here I separated the points of the original GPS track so it is easier to see that it goes back the same way: