iTunes full-screen video playback issue

Hi,

I have an odd problem with playing back videos (both rented and purchased) on iTunes, in full-screen.

It started when I rented and downloaded an old Disney film a few weeks ago.

When I started playing it, the audio was fine - and so was the image, until it went fullscreen and the controls faded away. Instantly the image split diagonally, with a thick black bar from top-right to bottom-left of the screen.

If I bring the controls back by moving the cursor/trackpad in any way, the image 'rights' itself completely, and carries on fine - until the controls fade away once more then the image corrupts again. The movie also played fine when not in fullscreen.

I deleted the download and re-downloaded, but it was exactly the same.

Then I downloaded one of my already-purchased movies into iTunes, only to find the exact same issue.

I have posted two screenshots below of a Charlie Chaplin film (why not!).

Online/Youtube movies and downloaded movie files are playing fine, but anything in iTunes is not, ever since this one rental.

I have had extensive interaction with Apple Support. Caches deleted, NVRAM / Pram reset, safe mode, running through a test account - nothing will make this problem go away.

I've also run a whole system diagnosis as advised by Apple Support - and have just heard back from Support saying 'this is something the engineers are aware of - it's not your hardware, they will hopefully address this issue in a future software update but we can't say if or when that will happen'. The advice was NOT to try a software reinstall.

So I am left unable to play any of my purchased iTunes movies in fullscreen, and no official certainty that it will be fixed soon, if at all. All my software is up to date.

I thought I would post here to see if anyone else is having this exact issue, or if anyone else can offer a fix - as you can imagine it's not very satisfactory being told that I simply can't play purchased content indefinitely.

Sincere thanks in advance for any thoughts/experiences/assistance. System/software details and screenshots below.

[ It's my first post so I hope I've put this in the right place. ]

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MacBook Pro (Retina, 13-inch, Early 2015)

Running 10.13.5 iTunes version: 12.7.5.9

2.7 GHz Intel Core i5 | 8 GB 1867 MHz DDR3

Intel Iris Graphics 6100 1536 MB