Bosch fridge/freezer (B22CS / Linea 300 series) began chiming and temperature flashing on the freezer side
I found the solution after digging up the appropriate manual for the Bosch B22CS30SNS)]2 online. Something was preventing the freezer from cooling, which triggered the temperature warning.

The temperature warning signal switches on if the freezer or the refrigerator compartment is too warm and the food is at risk of thawing.

Here are the steps I took to resolve the issue:

Exited alert mode: to do this, all I had to do was hold the alarm/lock button for two seconds or so—this showed me that the actual temperature inside the fridge and stopped the blinking
Reset: turned off the unit by pushing the power button on the top right of the door frame (opened the fridge and it's in the corner, near the hinge), waited a minute, and powered back on
Pulled out the large ice tray (just in case) and emptied out most of the ice (there was a lot)—when I put it back, I made sure it was fully inserted and flush
Got rid of any items that might have been blocking the freezer door—I didn't see anything obvious, but my freezer was pretty full, and I think this may have been the culprit
Closed the freezer fully, making sure the door wasn't even slightly being pushed open by an item inside
Just in case, I set it into &quot;Super&quot; mode which rapidly cools down the freezer or fridge over 6 hours
To do this, I pressed freezer and then super, which activated a quiet but audible change in the cooling system

Fortunately my food had not thawed yet and now it's on its way to being frozen again.
⚠ Careful with these fridges, because it isn't clear when the door is not fully closed
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