Shelf icons missing in Maya 2016

I have this mel-based script shelf in which upon the application closing of Maya 2016, when Maya is re-open again, the shelf tab is there, but the icons are missing.

Even if I click onto this ‘empty’ space, nothing is being run since it is empty. However if I switch to other shelf tabs/ open up the shelve-editor and back to the tab, Maya seems to reload it and this time round, all the icons are being displayed…

I tried deleting my userPrefs.mel, but the same thing happens and there are no errors or whatsoever appearing in the script editor…

Any ideas?