Recently, my dishwasher (Whirlpool ADG 9999M, about 10--15yo) stopped working with some standard error. After getting the manuals, I decided to inspect the drip tray: it was full of water. I removed/wiped most of the water and the dishwasher started working again. Now the tray is completely dry, but there's a lot of calcification build-up (see photos below).
Should I remove the build-up? And if so, how? Can I for instance use vinegar, or will it damage something? I can't really access most of the tray surface since there's a lot of stuff placed over it.
The reason why I think this can be related is that it has been suggested the drain pump may be blocked; the website says "remove and clean the pump", however, the pump does not seem to really snap off and I don't want to break something.
Photos: (1) the tray; (2) the build-up when I scratched it off and one place.