Automatic update bug in 3.9.2

I have set my wp-content folder to be “read” only permission and every time I need to update WP or install plugin/theme, I will be prompted for FTP username and password, which is what I want. However, this new update 3.9.2 somehow does not like this way. When I click Update Now button, the FTP username and password screen shows up, but only stay there for seconds and then quickly redirect (before I get a chance to enter my FTP credentials) to the page saying my WP has been updated to 3.9.1, instead of 3.9.2, then on the top of the page it says the automatic update failed, and asks me to update manually. It goes into a dead loop.

I finally had to set wp-content folder to be “writable”, then the update finished successfully. But I prefer to use my old way to update: only admins who know the FTP credentials are able to update WP, or install plugin/theme.

There must be some change in 3.9.2 update that messed up the manual update process.