The only ability upgrade I tried this with is businessman; and unless the bonus from that is already factored into the money gain displayed on the silver-upgrades screen ingame it doesn't work at all, so possible it is because the skill is broken. It was displayed as upgraded ingame, but as soon as you lost and went back if you checked it it was back at lvl1; not to mention that I doubt it worked.

I understand the idea behind the stress accumulation mechanic and that it is there to introduce sex scenes, but what if you would make the scenes rewards for achievements (have something fully upgraded, reach wave X, clear a total of Y waves, etc.); as said overall right now it does four things, and I don't think you should want any of them: It disrupts game flow, it makes it look like you get sex for performing badly, it makes it a chore and it punishes you for upgrading total max stress level

And another suggestion I forgot to mention: 

Please buff economic upgrades. Especially money per wave but also money per customer are both having the problem because the increase is linear and their cost increase isn't you quickly come to a point at which upgrading either will end with you at a net-loss. I mean if I pay 400g to make 5g more per wave that means I'd need to clear 80 more waves after that to make the money back; and while this is less bad with money/customer upgrades it still has the same problem: paying 3,8k or whatever it was again is not worth it, because you'd need to get another 3,8k customers afterwards to make that back - something quite unrealistic if you are at the point you will be at if you have to pay that much money for that upgrade. It would probably be best have a flat increase in the office upgrades but have a percentage increase ingame that also takes the office upgrades into account.