__________, the problem is nothing but a wrong assumption about processes.

'In other words' is a discourse marker used to rephrase or clarify a previously stated idea — to explain something in a different (often simpler) way. It fits naturally before a restatement like 'the problem is nothing but a wrong assumption about processes.' 'In the meanwhile' refers to time, 'Somewhat' indicates degree, and 'Engagingly' describes manner — none fit a restatement function.