I've had a similar issue with an FM23 save I carried over to FM24. I've always generated more than I've spent but I noticed in the previous season, when my finances were super healthy, the board asked me to work under a negative transfer budget. When I had a chance to negotiate the vision, they wouldn't budge on that issue, so I had to keep it. This meant I had to sell a lot of my promising youngsters in order to fund moves for world-class players to improve my squad. Yet after winning the Champions League and the budgets being set for the upcoming season, I was once again given a negative transfer budget to work with despite being over 450M in the black. I've attached the save game file of my most recent season after the CL final but before the budget is set (file name: negativetransferbudget).