Hi there,
Just wanted you to know, I experience the same issue. It only seems to happen for me after some alt+tabbing, and doing other stuff like watching netflix or browsing the internet while having Train Fever running in the background to let my cities grow. Performance is still horrible on large maps after like the year 2000, even though the most recent performance patch fixed it a little, so having it run in the background makes it less ‘annoying’.
My graphics card is a Radeon R9 290X. Omega 14.12 drivers.