I finally managed to get 6k chips, so I decided to do upgrades of my slots machines. The first slot machine I wanted to upgrade cost 630 chips. I had to click a few times to get it to take my click. After it did, it took apparently x times the click price, leaving me with 700 chips. Refreshing the page and logging in again did not update the chip count back. I did see many chips flying to my chip counter (although it actually deducted). If this was a sync issue with the server, there should be an built in safety preventing you from ending up to pay more than what is needed.