@noahlovell
First of all, I apologize for my English, it is not my primary language.
Hello, I’m solving the same problem.
Although it may seem that it’s a problem with a resolution below 320px, it’s not, it’s probably a bad evaluation of the conditions whether it’s a mobile device or not. I’ll try to explain it to you properly, including specific problem phones.
I encountered a problem with displaying a website created in wix studio on some mobile phones. Specifically on the Galaxy Z-fold 5 and Samsung A15, huawei p15, huawei P smart 2019.
The thing is that the layout that is set in wix studio for mobile display is not displayed on these phones - so the columns do not wrap under each other, but it is displayed as in the desktop layout. The problem is not just in one section, but the entire website is broken like this, including the header - it is also displayed as a desktop one. It works on most phones, but not on some. It simply tries to cram the desktop layout into the phone’s resolution, so the columns are insanely narrow and the text overflows from them. I managed to simulate it in devtools - it happens when I set a responsive resolution and reduce the width below 320px - suddenly the mobile layout stops showing and exactly what I described happens. But these phones definitely do not have a resolution below 320px, I thought that the z-fold was an exception, that there might be some problem with how it can be folded, but it is also manifested on 3 other phones.
It is also necessary to mention that the problem does not appear on all galaxy z fold 5. For one customer it is broken and for another with the same phone and browser it is displayed correctly.
I wonder if the problem is that it is evaluated according to user agent strings? Because they can be different even on the same phone model? I do not know what you decide based on, but it does not always work correctly. I need to solve this on the website for the client, it is really a problem.
The z-fold has a resolution of 2176 × 1812px (inner screen CSS width is roughly 690 to 928 px (depending on screen zoom) by ~700 to 1080 px tall. The cover screen CSS viewport is narrower, typically 340 to 360 px wide by ~740 to 800 px tall.), the samsung A15 has a resolution of 2340 × 1080 (CSS viewportu 412 × 892 px), huawei p smart 2019 is 2340 x 1080 - certainly not below 320..
You probably have a poorly targeted recognition of the mobile device - because it recognizes it as a desktop screen. Please advise what to do with it, I don’t want to pay for a non-functional thing. 
It turns out that this is not just my problem, I found a lot of threads where people are solving the same problem.
I can attach only 2 images
You can check live web on mobile device and on desktop:
incorrectly displayed desktop layout on mobile device Samsung A15 (same as on galaxy Z-fold 5 and huawei):
