[ubuntu] Strange problem with Dolphin file manager

Hi,
I am ruing Ubuntu 16.04 and using Dolphin File manager version 15.12.3

When I click the "Find" button to search for files by name on my hard drive, I get no results shown.... this despite their being files that meet search criteria.

If I try to search an exteal drive (coected via USB) results are shown. I find this a bit odd to say the least.

I know there have been issues surrounding searching from within Dolphin and I recall when using an earlier version of Ubuntu (14.04) the default "inteal" file indexing ahd to be tued off to enable Dolphin file search to work.
I can't seem to see how to do this in 16.04. Can anyone point me in the right direction or offer any solutions to the problem please?

Obviously, "find" must be enabled within Dolphin as it is able to search my exteal drives but I caot get it to search my inteal hard drive..

Kind regards, Pat.