I can't submit this, as I can't make it repeatable, but it happened several times today.
I created an object, then did a Linear Copy. In Paper space (set to Quality and marked to Render for Print Only), one of the objects (the original, not a copy) did not render. It was visible in Wire Frame mode. I deleted the object that did not render and copied the copy back to the first object's place. Still invisible when rendered.
And the exact same problem happened with another object that had identical copies.
The only solution was to change the Viewport to render all the time, then change the Viewport to Wire Frame, followed by Hidden Line and then Quality. It is possible I didn't have to use Hidden Line in that sequence but, as I said, the bug isn't repeatable with any reliability.
TC Pro Platinum 2019, 2018, 2017, 2016 & 2015 (all with LightWorks & RedSDK) & V21
System: i7-5820K @ 3.30GHz, ASRock X99 Extreme4, 16GB DDR4-2133 RAM, Gigabyte GTX 970, Samsung NVMe SSD 950 (256GB), Windows 7 Pro (64-bit) SP1