In such case you can try:
FString FormattedErrorMessage;
if (ErrorMessage.Len() > 0)
{
int32 Size = snprintf(nullptr, 0, TCHAR_TO_UTF8(*ErrorMessage), \* your variables here*\) + 1;
char* Buffer = new char[Size];
snprintf(Buffer, Size, TCHAR_TO_UTF8(*ErrorMessage), \* your variables here*\);
FormattedErrorMessage = FString(UTF8_TO_TCHAR(Buffer));
delete[] Buffer;
}
UE_LOG(LogTemp, Error, TEXT("%s"), *FormattedErrorMessage);