I think something went wrong when using the last update. I had a save with Version 1.1.1 with quite some investments, when I passed my save to Version 1.2.0, I quickly ended up with 3 million denars in about 20 days ? Maybe if my weekly dividend was X, instead of becoming X / 7 it just stayed as X ? I don't know.
When I loaded my save, I started gaining about 50,000 denars per day. When I think I was gaining that per week before the update, not per day. Oops.
Maybe if I start a new game I won't have that problem, I think it might be related to using a previous save with the previous version, not sure. Can't confirm but never made that much money before.