iframe issue 1.7.5

[Rumbuilder]

Here's a thread from PS github that was no help - I'm desperately trying to get this resolved asap.

https://github.com/PrestaShop/PrestaShop/issues/12135

Thank you!

 

I have checked everything I can, server is compatible, settings are correct, etc.
Finally bit the bullet and did they're last option - I did a COMPLETE wipe of the installation, and a BRAND NEW installation - TWICE. The first time I used the autoinstaller in the PS zip file(via index.php)
I then attempted to modify an EXISTING demo product, and add my own iframe to the product description. (I enabled iframes in settings, and also disabled html cleaner). THIS WORKED FINE. My content displayed, no issues.

I then created a NEW test product, cloning the information from the demo product EXACTLY. Then I added my iframe code, exactly the way i had before. GUESS WHAT!? I get the "Unable to update settings". Console throws:
VM798:1 Uncaught SyntaxError: Unexpected token < in JSON at position 0
at Function.parse [as parseJSON] ()
at Object.error (form.js?1.7.5.0:687)
at u (main.bundle.js:275)
at Object.fireWith [as rejectWith] (main.bundle.js:275)
at i (main.bundle.js:275)
at XMLHttpRequest. (main.bundle.js:275)

I then tried wiping everything AGAIN, and using the Softaculous Installer via cPanel, did the exact same tests, and got the exact same results.

Anybody have ANY idea what the cause could be? I've checked everything I can think of, and I have not modified any core files, or heck... ANY files, and have tried this TWICE from a completely clean install, with ZERO resolution.

I appreciate any help possible, I have a functioning store that I need to have up and running asap.

Thanks.