Q: OS X Yosemite 10.10.5 have been installed recently , but the history states but the history that it has been installed 4 times in the previous 30 days ,how does affect functioning ,if there is a problem how can i uinstall the previous?

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Some users are experiencing issues with the OS X 10.10.5 installation, so they couldn't install it from the Mac App Store. Instead, it had to be done through the Combo installer that can be downloaded from the Mac App Store.

First of all, open the Apple menu -> About this Mac, and tell us which OS X version you are running:

• If it is 10.10.4 or older, download and install the OS X 10.10.5 Combo installer -> OS X Yosemite 10.10.5 Combo Update
• If it is 10.10.5, don't worry. The update wasn't installed all the times the Mac App Store says.

App Store Update Problems  see Linc Davis’s answer.