Hello,my name is Rick
I will assist you tonight
It sounds as though you may not be getting all the power the unit needs
I would like you to reset the breaker
I also need to know if you have a meter to check voltage?\
Once you reset the power, if the unit still will not heat normally, we need to check the power connection to the unit, all you need to do is remove the cover where the power cord is attached.
Pull the unit from where it is setting and check the power cord please
you are looking to make sure all your connectors are not burnt
take your time
Where did you see the sparks
there should be a access panel to remove so you can see where the power cord connects to the unit, open panel and tell me if you see any loose connections.
Of course unplug it first
Im glad we were able to locate the issue for you. Please remember to rate my answers before you leave.
Have a good weekend. Enjoy the cabinet.