By Guy Taylor National Express owner Mobico’s shares tumbled this morning after it lowered its annual profit forecast amid ongoing audit issues affecting its German rail business. The transport group said it expected 2023 adjusted earnings before interest and tax to come in at between £160m and £175m, compared with a prior forecast of £175m and £185m. It will also take a £70m increase to the “onerous contract provision,” plus an additional £25m, it said in a statement on the London Stock Exchange. Shares were down over eight per cent in early trading. The issues mean the announcement of Mobico…