Temperature too cold even when on lowest

Set the temperature at the lowest point in the fridge.

freezer should be -15 and that is about 4-5 c on the knob
fridge should be around 4-5 C which is around +3 C
frost build up is from door opened too often , for too long or bad door seals
It is more prevalent when the ambient humidity is above 50% as it is the water vapour in the air condensing on the cold surfaces

The temperature control thermostat, alson known as the colds control thermostat has gone bad and basically isn't converting electrical/temperature signal properly and needs to be replaced.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/jason_4570d45317834dd3

Veggie can freeze easy when temps are incorrectly set within the unit. Check temperature setting for both sides of the unit. Due to physics cold air drops and heat rises. With this in mind, make sure door seals are tight around the doors, if this does not solve the problem, you may need to cut off the direct air flow into the veggie bin directly to solve this issue. Over the years I have seen reducing air flow calms the freezing issue.

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turn both control to the same number the lowest number and then wait 24 hrs if you want it needs to be cooler move both controls 1 number then wait 24 hrs and see if you are happy

Lower the settings to 1 or 2. If you have veggie bins with the sliding adjusting air vent (door thingy) check them and make sure the settings are cold and not colder. it brings more air to the bottom. Cold air drop to the bottom because it is heavier than warm air.

Most fridges have crisper drawers that have a selection lever on either the front or side of the drawer that allows you to select eiher veggies or meat. Veggie setting is supposed to keep the crisper drawer warmer, while Meat setting makes it the coldest possible.

If you don't have the selector slide levers, I would suggest you use the highest possible crisper drawer available, as the lower in the frdge compartment you go, the colder the air will be. That should resolve the problem you're having, other than lowering the fridge temp setting slightly.

You might notice a cold air exchange vent next to your crisper, which supplies cold air from the freezer section into the fridge section, so that could be contributing to the colder temps in the crisper where you keep your veggies.

Hope you find this Very Helpful and best regards!

I have dealt with bosch and thermador quit a bit and they usually don't have to much of a recommendation for these settings because they are more of a commercial type appliance producer and all situations are different. Here is a tip for the sliders though. Remember that leafy produce needs more airflow to hold its texture and taste and anything with a skin requires less airflow. As far as the temp settings I believe the most nominal settings are going to be in between 5 & 7 to keep from freezing the produce. You will have to play around with it a little though to get it to keep the ref good and cold but keep from freezing the vegies. Hope this helps. Good luck.

1 is the warmest setting, 7 is the coldest.
No answer for your veggies freezing.