This is probably related to the labyrinth being polluted with sludge (it’s the most common cause in this type of dishwasher). Quite a lot of Bosch dishwashers have this problem, but luckily it’s fixable without paying for repairs.
What happens is that the switch for the bottom compartment fails to trigger the pump. Once that one fails to trigger, the fallback will, which will shut off the cycle to prevent flooding the house, which is actually quite a nice feature :) This switch is normally triggered by a small floater, which is most often embedded in the labyrinth. The labyrinth is where all water flows through, and over the years can get accumulated sludge in it. Normally this isn’t a problem, but the floater can get sticky, and therefore no longer respond to the changing water level. Washing on higher temperatures makes it ‘unstick’ for a while, and trigger the pump as it should. Cold rinses just make it stick better.
The labyrinth can be found on the outer left side of the dishwasher, so unfortunately you need to remove it from it’s enclosure if it’s a built-in. Remove the left side panel, and you’ll find a large part of slightly opaque white plastic. This is the labyrinth. In there should be a small (probably red) floater. Prepare a few liters of scalding hot water, with a dishwasher tabled solved in it. Using a small funnel or a small watering can, rinse the floater with the prepared solution. The labyrinth will drain itself, and the system should not flood, but keep towels handy just to be sure. Once you poured a few liters you should see the floater start to move freely again.
Test the dishwasher while still open, and verify everything is in expected working order before building it back in.
Good luck, and please let us know if it’s fixed by this or that we need to dig a bit further.