Toaster option is not working (model TO1560BC).

Hello! The toaster option of my Black & Decker toaster-oven (model  TO1560BC) is not working anymore. I opened it and tried to fix, but couldn’t find yet the source of the problem. I also observed that the upper resistance becomes hot way faster (and keeps this rhythm) than the bottom one. Don’t think that there is a link between this observation and the toaster problem, but I mention it in case someone thinks that there is a link.

Thank you in advance!