Issue with Image Insertion in WordPress (Only on Sub-Accounts )

I have this issue (detailed more here https://www.inmotionhosting.com/support/community-support/wordpress/cannot-insert-more-than-2-images-at-a-time-into-wordpress) that I have been going back and forth with InMotion about for weeks. This morning I ran multiple tests and was able to isolate the affecting scenarios (at least on my end, since InMotion techs still say they cannot replicate on their end)

THE ISSUE: Cannot insert more than 2 images at once into a Wordpress post. The upload is fine - the issue happens on insertion. Support cannot replicate - although regardless of what computer or internet connection I use I have the same result.

FINDINGS:

1. All sites migrated from Site 5 last month using a control panel migration have the issue (may or may not be relevant after my findings today, next)

2. Only sub accounts on InMotion hosting have the issue

3. I installed a WordPress site on the main account site using Softaculous and an FTP upload installation and it did not have the issue.

4. On a sub-account I disabled all plugins on an existing account, and could not still insert more than 2 images at once.

5. On a freshly installed Wordpress on a sub-account I could not insert more than 2 images at once.

ISOLATION RESULT: (on my end)

Only happens on sub accounts of my hosting

Plugins are irrelevant to whether it happens or not

Softaculous install vs. FTP install makes no difference

The primary domain on my hosting account is unaffected

So, I am wondering if it is possible it has something to do with package settings or how sub-accounts are set up? I am on the R-2000S reseller hosting plan.