FinanceShell's share buyback plan in jeopardy amid cash flow concernsAnalyst warns tax payments and 'other items' weigh on supermajor in fourth-quarter updateBuyback problem? Wael Sawan, Shell's chief executive, taking part in a panel discussion during at a conference in Abu Dhabi in October 2023.Photo: AP/SCANPIXIain EsauAfrica CorrespondentLondon