South Korean firms with factories at a recently resumed joint complex in North Korea continue to face challenges in normalizing their operation, market watchers said Thursday, as a five-month hiatus dealt a harsh blow to their liquidity and credibility with buyers. The analysis came after the inter-Korean factory park, a rare symbol of detente and economic ties between the two war adversaries, reopened last month after a five-month hiatus. The Kaesong Industrial Complex, in the North Korean border town of the same name, was unilaterally shut down by the North in early April amid heightened military and political tensions on the Korean Peninsula.