This road seems to be incorrectly setup, it allows for routing of vehicles which may be correct but because there is no speed limit it prefers routing via this route.

https://maps.openrouteservice.org/#/directions/10.6550661,51.2440366/Kleines%20L%C3%A4dchen,Rehungen,TH,Duitsland/data/55,130,32,198,15,97,4,224,38,9,96,59,2,24,5,192,166,6,113,0,184,64,70,0,24,3,160,13,128,86,115,13,52,252,1,167,63,98,2,96,5,149,194,6,97,160,110,35,143,38,208,135,0,156,12,154,112,1,193,211,128,118,78,32,232,128,128,1,213,60,8,137,176,229,0,11,202,0,91,92,249,201,41,93,2,0,51,120,0,109,210,225,11,26,60,0,110,72,3,152,5,163,12,154,34,144,230,232,150,232,208,232,136,96,246,120,161,144,6,6,97,176,232,176,254,6,200,0,30,240,6,0,174,6,0,250,152,42,232,137,184,146,132,74,170,234,154,218,160,200,46,16,240,176,57,42,16,54,0,158,238,149,184,160,168,45,5,14,0,178,153,54,234,0,10,205,109,154,254,144,48,8,40,24,218,0,218,0,186,0,190,74,53,117,13,193,104,153,161,11,32,193,208,206,88,32,43,203,203,64,0,0

This off-ramp trunk road has no maxspeed, causing it to be a faster route than staying straight on the trunk road.

It's fixed on my side by using a speed limit of 80, but for cars that can go 120 this off-ramp is still faster to take.
https://maps.openrouteservice.org/#/directions/J%C3%A4dekamp,Hanover,NI,Germany/Am%20Leineufer,Hanover,NI,Germany/data/55,130,32,198,15,97,4,224,38,9,96,59,2,24,5,192,166,6,113,0,184,64,78,0,232,3,96,25,159,1,216,1,96,17,134,128,56,2,101,49,139,92,96,26,1,89,28,54,174,187,22,160,1,148,149,42,149,24,6,226,38,66,141,98,197,27,16,86,210,151,110,189,104,86,27,170,189,97,197,133,81,220,68,7,16,16,0,58,167,129,17,54,28,160,1,121,64,11,107,134,133,11,87,160,64,6,111,0,3,110,139,130,11,13,15,0,6,228,128,14,96,11,70,12,141,14,98,11,238,143,238,141,14,136,134,10,23,141,153,6,230,227,155,14,139,10,150,236,128,1,239,6,224,10,230,224,15,169,133,110,142,89,227,79,128,11,237,212,0,0