Before leveling bed , here are some suggestion for reference.
1.You may check if the two sides height of X-axis whether are the same .
We need to make H1 equal to H2.
2.We need to check if the two quick- removal nozzle kits is installed .
If not , you may install it well .
3.You may check if the around of nozzle has defective filament .
If yes, you may preheat the nozzle and clean it .