Why is the update button in "App Store" app opening the app instead of updating it?

I am experiencing a problem with updating my apps on all of my Apple devices: iPhone 5s, iPad Air, iPhone 4s, iPad 3

They are all running iOS 7.0.4 (11B55a) jailbroken using evasi0n and this problem has only recently started happening.

To update my apps I normally go into the "App Store" app down to "Updates" and then manually press the "UPDATE" button to update that app. Since the 10th October pressing the "UPDATE" button causes the app to be loaded instead. I went to try this on my other devices and got exactly the same result. This is odd because some of the devices haven't had any Cydia or App Store updates for ages.

I have attached a screenshot of what my update screen looks like on my iPhone 5s:

You will notice that:

• Update All is greyed out although it does start off blue for a split second before going grey.
• Apps updated on the 8th October correctly show the "OPEN" button.
• Apps updated on the 10th October incorrectly show the "UPDATE" button.

I have tried the following, but none of these have worked:

• Turning off WIFI to use 4G instead.
• Restarting the iPhone 5s.
• Signing out and logging back into my Apple account on the iPhone 5s.
• Syncing the iPhone 5s with iTunes on my Windows PC.

I have tried the following which does work, but doesn't make any sense:

• Pressing on the app icon to expand the description and again to load up details of the app. The "UPDATE" button on the app detail page works for some reason, but strangely keeps prompting me to put in my password for my account.
• When loading up "App Store" and pressing in the top right "Update All" quickly before it is greyed out actually starts the update of all apps.

In summary there are 2 problems that are happening:

• Trying to update an app from the main update screen loads the app.
• Apps that have been updated show the wrong text for the button "UPDATE" instead of "OPEN".

Does anyone have any suggestions as to why this is happening now? I have previously been updating fine before the 10th October.

Seems like I am not the only one experiencing this problem:

• https://discussions.apple.com/thread/6591839
• https://discussions.apple.com/thread/6590253

1. Go to Settings -> iTunes & App Store -> AppleID -> Sign out.

2. Close the App Store app (double-click home button, swipe up on App Store), and restart the phone -- but instead of holding the power button and shutting down "cleanly", hold the power and home buttons until it powers off. Power it back on.

3. Settings -> iTunes & App Store -> Sign In. See if you get the same results.

If that doesn't do it, try deleting the affected apps, then shutting the phone off cleanly, then starting it back up and re-installing the apps.