Premiere to Media Encoder hates white PNG with alpha

I've looked for people that have had the same problem, but haven't been able to find one yet. Here's the issue - when exporting a sequence using Premiere Pro (nothing fancy...straight video with no effects with b-roll and my company's logo over the footage for product reviews), I have no issues - export is perfect. But the problem comes in when I try do export the same thing through dynamic link with Media Encoder. When I start the encode, the first few seconds are perfect, but when I get to the first edit, the color goes weird and the image freezes. Check out this screenshot:

I've been able to track the problem to the PNG file that is the white (correctly colored) logo in the bottom left of the screenshot above. The problem starts when that PNG file begins on the timeline (I know this because if I remove that PNG altogether, AME works fine). I've been using that overlay bug for the last nearly 6 years with no problems, but when I upgraded CC to 12.1 a couple weeks ago, it started giving me issues. A couple other things that I've noticed:

- other PNGs work just fine, including the colored version of the same logo

- adding the logo with AME's effects/image overlay command does the same thing

- it happens to other sequences in other projects with the same white logo, but this is the first time in almost 6 years this has happened

- I tried recreating the image in photoshop by resizing and relocating an image and renaming it something else, but it still won't work

- I also tried using the color version of the logo and using the color overlay in PS to make it white, and it still failed

- I'm on a Mac using the fully-updated CC software (for now) on OS 10.12.6

It's clearly something to do with the PNG, but what changed inside Media Encoder to make this not work? Why will it not work when it's got a white overlay, but the original full color version is fine? I really don't want to have to change the file type since I use this file in pretty much everything I do and reconnecting them all will be not so fun.