Alpha channel transparency issue with Premiere Pro CC 2018 v.12.1.2 (Build 69)

We are having issues with PNG and JPG files being transparent in Premiere Pro CC 2018 v12.1.2. We need a seamless cross-platform workflow using PNG or JPG images. 

We have begun production of an 2D animated episodic children's TV series.  We're using Storyboard Pro 6 to draw the storyboard panels/images, organize them into scenes/sequences on the timeline, and then export sequences using SBP's Conform FCP XML.  We are using Premiere Pro CC 2018 version 12.1.2 to edit storyboard animatics, and for both offline and online editing.  Storyboard Pro exports a conformation FCP XML that contains images and audio files.   When I import the FCP XML into Premiere Pro, the images are black--ie. transparent.  I tried exporting a Conform FCP XML with PNGs and then tried with JPGs, both had the same issue of not being visible when the XML is imported into PPro.  However, captions (text of script dialogue, action notes and scene numbers appear as a title banner at bottom of screen) layers are visible.  All of the Storyboard Pro panels are exported as nested clips containing the background layer, and 2 or 3 transparent layers for props and characters drawings.  Also note, red drawings or drawings other than black or white are visible.  Neither black or white are visible.

In Photoshop, I opened a PNG file, from within the XML export folder and found that it is black/not visible.  I opened the XML export folder containing PNGs  in Adobe Bridge to view all the panels at once.  All of the PNG files seem to be alpha layers (including the BG layer);

In Adobe Bridge, I opened another XML export folder containing JPG files, since JPG files do not contain alpha channel or chroma key information, I thought that they would be visible/not transparent, but they were not visible.

I found several posts on PPro forum regarding alpha channel png issues.  https://forums.adobe.com/message/10307067#10307067

It seems that this issue has not been fixed by Adobe, as the last entry in the forum states: "Sadly, the solution to this is converting your PNG's to TIFFs. Its a pain, but it solved my problems.  Just wish Adobe's Twitter support told me that. Versus the stock "a fix is coming" response. Thank god for these forums and you guys."

We are working with thousands of images in a single 22 minute storyboard. As such, a seamless cross-platform workflow is paramount. We'd like to use PPro, but if this issue cannot be resolved we may need to use Final Cut Pro in order to achieve the productive workflow that we need.