It's caused by the money duplication. To get around it somewhat, just keep going up to the next egg until you can just have a few chickens making money and wait until you can make the purchase off of earnings, by buying multiple levels of those upgrades at once.
This. Also the unlimited money seems to break after a while and cant purchase any fleet or hen house upgrades.
Don't want to sound ungrateful though, thanks for what's working right now.