There is a logic bug that can occasionally be triggered when injecting code in some PE files while using the GetModuleHandle/GetProcAddress IAT handler.
In that case, Shellter may use the unicode version of GetModuleHandle with an IAT Handler stub dedicated for the Ascii input version version of it.
This will cause the infected application to crash without executing the injected payload.

Fix is due to be included in Shellter v6.5.

Cheers,
kyREcon