LONDON — Britain’s Brexit minister predicted Monday that relations between the U.K. and the European Union would continue to be “bumpy” amid tensions over post-Brexit trading arrangements. David Frost said talks with the EU on ironing out the problems were “not hugely productive” so far. “I think it will be a bit bumpy for a time, but there is a lot of business to be done,” he told the House of Commons European Scrutiny Committee. Since Britain made its final economic break from the 27-nation bloc at the end of 2020, the two sides have sparred over EU boats’ fishing rights in U.K. waters and new trade arrangements for Northern Ireland.