Not Rendering/finding clips

Environment: OS X 10.13.4, FCPX 10.4, Final Cut Library Manager | iMac Pro 8 core, 64GB ram 1TB SSD, 2nd 27" cinema screen | Promise Pegasus3 24TB via TB3, Synology DS1815+ with 52TB space, 1Gbps Ethernet

Scenario: I am trying to manage storage space, by changing from all source inside Library on Pegasus, to storing source media on the NAS. So I open a Library with say 1TB of source, go to the Inspector and change Storage Locations from In Library to Choose (NAS location). I then Consolidate Library Media. This correctly moves Final Cut Original Media folder to the NAS and puts links in the Library.

Problem: This doesn't always happen(!), but it does happen: Project file in timeline, now shows red screen with yellow Exclamation and cannot find source clip. HOWEVER if I click Shift+F to go to source file in FCPX, it identifies the correct clip, which IS available!!! I can play this clip, and I can Reveal in Finder, and the play the source using QuickTime! In the Timeline, I see the dots for unrendered content, but selecting Render or Render All doesn't fix or change this.

Any thoughts???

Problem solved - after posting my description, I noticed in FCPX a message that plugin Flicker Free was unavailable. I had previously purchased this from Digital Anarchy, but probably when moving to my new iMac Pro, the registration didn't transfer properly.

When I re-installed the problem went away! HURRAH! Hope this may help someone else in similar situation.