I was buying 50 infra for one of my cities. I had sufficient money. When I clicked 'Go' on my city page after entering the value, the web page indicating heavy server load came up (The 'Politics and Snore' one). Then I saw the money for the purchase had been deducted, but my infra level was the same. My city was at 1100 infra (and still is), and my money had reduced by ~400K-ish after this little bug.
No screenshots, unfortunately.