Check if Toolkit -> Disable seasonal closures. That lets you show/hide road closures as well as seasonal stuff.
Ticking it will ignore any traffic/road closure info, and therefore tell you if there's some sort of closure that's causing the route to re-calculated to go around the problem.
If it is, go to https://www.roadworksscotland.org/ (or https://one.network in England and Wales) and check what the closure is and whether it affects the time you'll be travelling.
From a quick scan, it might be this (but no guarantees):
SW100-02106101/CSD (4137262)
Church end cottage Durness IV27 4PZ
A838 B801 Junction Rhiconich - Rispond Road Junction, Durness
Scottish Water
0800 077 8778
0345 601 8855
help@scottishwater.co.uk
www.scottishwater.co.uk
[Start date] 01/09/2026
6 Working Day(s)
REPAIR BURST MAIN
Maybe they finished early!