You receive an "unable to load" DLL error when running forms. It can reference any DLL on the server.
Winshuttle SAPIS relies on 32 bit SAP GUI files to communicate with SAP. Windows Servers reserve the %systemroot%\system32 folder for 64 bit applications. So when SAP GUI attempts to run DLLs from the system32 directory, Windows redirects the application to the syswow64 folder instead, where 32 bit versions of the necessary DLLs are kept.
SAP DLLs in particular, are notororious for having a bit version in the name, like librfc32.dll, but actually having two different bit versions of the DLL so there is a librfc32.dll 32 bit and librfc32.dll 64 bit. There is no way by looking at these DLLs to know which version is 32 bit and which is 64 bit.
The "Unable to load" error is usually an attempt of the application to force load the wrong version of the file (such as 32 bit version of librfc32.dll being placed in the system32 folder) or vice versa (attempting to load a 64 bit version of librfc32.dll in the syswow64 folder).
Ensure the right DLLs are in place and be careful with re-installs of application on the server. Re-installing SAP GUI may revert the DLLs in the system32 folder back to their 32 bit versions.
If you have a working environment, you can copy the DLLs from that environment and overwrite the current files in the failing environment.