Sallaw

I did a 7 hour print successfully. After that I started a new print immediately. First everything was ok, but after a while nozzle didn't extrude material properly. I stopped the printing. After that print core aa didn't cool down (it stayed 175c and just said "waiting"). So i booted the printer. I unloaded material 1(pla) and loaded the same material back. In loading The material came out from the nozzle end (maybe little bit thin). After confirming the loading of the material printer started to cool down the print core aa. It was again stuck for maybe 15minutes and didn't cool down (said "waiting" in the printer). I booted the printer again and waited for the cores to cool down to 40c. After that I tried to start printing and cura was stuck in preparing phase for a half hour and it didn't start printing. The temperature of the core aa was around 210c all the time. II had not other option the to boot the printer again. Is there a problem with the cooling or why is it just stuck in preparing phase?