Buses going way out of route

As you can see in the first image, I have buses simply leaving their routes and going through a longer random route that is not their designed one. The black arrows point to four buses that gone rogue and left their (blue arrow) routes. It's happening continuously, wasn't a single moment when I took the screenshot.

Second image shows a bigger picture including from where they're coming (immediately before going rogue, red circle) and to where they're are going (blue circle). Red path are their designed route, orange path is what they're doing (it looks like they're are separate in the beginning, but it was bad drawing from my part, they split when red goes west, then orange keeps straight north)

It started when I bought this new tile north and started building there. If it makes a difference, up north, next to the airport in that pink dot is where a highway starts and goes west, while the whole red path is a highway. Both have exclusive bus lanes.

So, finally, what the hell is happening and is there a solution? Right now it's not causing any issue (apart from realism), but when I keep in building in that north tile it will cause unnecessary traffic and jams, that's why I wanna try and solve it now already.

Thanks everyone :)