LONDON—European bank stocks tumbled again on Monday as more financial firms cut ties with Russia and others braced for further impact from the country’s invasion of Ukraine. Lenders and investors with links to Russia have been cutting ties to the country as Western sanctions have been brought to bear, while others have sought to reassure their shareholders that the direct impact could be contained. French asset manager Carmignac and British professional services firm EY became the latest on Monday to say they were severing links. Carmignac said it would not buy Russian securities and would divest from existing assets, while EY said it was axing links with operations in Russia following similar moves by rivals KPMG and PwC. The escalating crisis is also causing upheaval at the top of companies, with multiple board members at Russian firms including the British chairmen of gold and silver producer Polymetal and metals and …