I just had a similar issue, I'm in season 2032/33 with my Real Madrid save, we recently just moved to a 122k capacity stadium. Club value was 1.48billion, just checked it after 4-5 games into the season and its down to 130million. It still says I'm rich. I'm making a profit each month of about 3mil just my club value dropped.
I would'nt mind so much if it was due to bad financial management on my side, but I've cut costs majorly and won every single competition available. I wont super cup, european super cup, league, club world cup, champions league and spanish cup in the previous season. I have 19million debt from my stadium move which is due to be payed off in 2035. Its pretty annoying since I've put so much time and effort into making such a major club so financial stable and still so dominant