When I started at my first company, they had a very complex VB application running on dozens of customers around the country, each having some particular needs of course.
There was a LOT of global variables (seemingly random 4 uppercase letters) controlling everything.
At some point, the application had some bugs which were not appearing when the application was run in debug mode in Visual Studio. The solution was obvious: installing Visual Studio for each customer on site and teaching the users to run the app in debug mode from Visual Studio. I don't know how they convinced the users to do this and how they managed with the license but it was done.
What happened next was even worse.
There was no version control of course, the code being available on a shared disk on the local network of the company with the code copied over in multiple folders each having its own version, with no particular logic to it either, V1, V2, V2.3, V2a, V2_customer_name, V2_customer_name_fix, ...
After that, when there was a problem for a customer, the programmer went there to debug and modified the code on site. If the bug/problem was impacting other customers, we had to dispatch some guys for each customer to go copy/edit the code for all of them. But if the problem was minor, it was just modified there, and probably saved on the shared folder in some new folder.
What happened next was to be expected: there was no consensus on what was the final version, each customer having slightly different versions, with some still having bugs fixed years before for others.
At some point, the application had some bugs which were not appearing when the application was run in debug mode in Visual Studio. The solution was obvious: installing Visual Studio for each customer on site and teaching the users to run the app in debug mode from Visual Studio. I don't know how they convinced the users to do this and how they managed with the license but it was done.
What happened next was even worse.
There was no version control of course, the code being available on a shared disk on the local network of the company with the code copied over in multiple folders each having its own version, with no particular logic to it either, V1, V2, V2.3, V2a, V2_customer_name, V2_customer_name_fix, ...
After that, when there was a problem for a customer, the programmer went there to debug and modified the code on site. If the bug/problem was impacting other customers, we had to dispatch some guys for each customer to go copy/edit the code for all of them. But if the problem was minor, it was just modified there, and probably saved on the shared folder in some new folder.
What happened next was to be expected: there was no consensus on what was the final version, each customer having slightly different versions, with some still having bugs fixed years before for others.