InstallShield 5.5 fails to open in any capacity, has anybody else seen this?

So I'm not here to troubleshoot really I've fixed this issue, I'm just curious if others have seen this before, and if somebody might be able to provide a bit more of a reason as to why this happened.

Here's the full story:
I work for an IT consulting firm, and one of our enterprise clients(AKA massive and we keep separate staff on-site for them), and I was called from the main office because software wasn't installing and it was assumed to be an imaging issue. I tested the image, as well as a fresh install of Windows, and only this ONE SPECIFIC workstation wouldn't run these installers based off InstallShield 5.5. Any other computer, ANY, will work just fine, even the exact same specifications just a different model. Here's the full list of things I ended up doing for troulbleshoooting, and below that will be how I made it work. I'm curious if anybody has insight into how it got this fucked up.

  1. Reimage workstations. There's about 500 of them and I tested with multiple
  2. Verified the installer was not corrupted. It was also working on other models
  3. Removed AV and Encryption software.
  4. Fresh install of Windows 7 x86 Enterprise with stock drivers from manufacturer's website
  5. Update the BIOS.
  6. Rollback of Windows Updates
  7. Verifying updates were all installed.
  8. Called the Vendor. The Vendor was unable to get it to install and suggested an upgrade(not an option).
  9. Ran Process Monitor. The results from Process monitor gave little information besides the error "File Locked with Readers Only" on setup.exe on occasion, however this seems to be normal to appear.
  10. Compatibility mode
  11. Windows XP Mode(not compatibility mode). This actually works, however it would have been an EXTREMELY last ditch if we had no other option it needed to be avoided at all costs.
  12. Forced installshield to create a log using command-line, which did not work.
  13. Event viewer reported no errors.
  14. Cried begged and screamed for it to start working. Unfortunately this one got me nowhere.
  15. Suggested using a different model. Of course this got rejected immediately.
  16. Gave up for a day. Cause I had other things I had to work on.

Read the procmon logs again, and from a successful install. While this may not seem as extensive as it seems, the log was over 1.5 million items in the end, with a total size of over 550MB in the end. I manually ran through the entire log(with a bit of filtering for services that were unrelated), and found a file that was used to install all the registry keys in the logs. Of course I couldn't find this file and freaked out and threw a massive fit as it was 10PM at night. I did another hour of searching the logs and files, and found this random setup.exe in a folder by itself. I copied this installer into the setup folder of the application and it worked. IT WORKED! At this point I copied it to all the other installers and it also worked. Turns out InstallShield uses a generic installer.

I'm just curious, since I spent over 16 hours on this, if anybody knows what ended up causing it. I was able to resolve the issue Friday, it's purely my curiousity.

What CPU's are in the effected machine/s - If I remember correctly intel had some hinky shit with instructions sets in a few of their cpu's - where specific code would either fail to run or cause a hard stop. Unlikey what is happening here but worth investigating.

I believe it was the i5-6600, 8GB of RAM(1 stick), built in graphics.