I've been playing the game with no issues to performance until the latest beta update a few days ago, that being the v1.14.9.23668 / Sep 12 build* and the game has suddenly started to lag when I'm close enough to lay track.

I would typically get a framerate of around 60 - 80fps prior to this update, sometimes higher, but now it could be as low as 5fps. The average at the moment seems too be around 10-15fps. This also gets worse if I open the mod menu or adjust a station near a busy area. To say it turns into a slideshow would not be an exaggeration.

I've tried multiple PC restarts, opening different saves with fewer trains running, reducing the (already low) settings and waiting a few days, yet nothing seems to have worked. Any investigation into this would be appreciated. Also again, I doubt this has anything to do with my PC specs since I was playing NIMBY in the morning of the day before it updated with no issues prior.

*EDIT. Just bumping to say that this issue has not resolved itself with the latest update, 1.14.10.

EDIT 2: Downloaded the latest beta, still not fixed and if anything, the lag is even worse.
Attached is a video showing how bad it gets:
https://www.youtube.com/watch?v=RX5R7RQm6NA