Melting plastic smell from oven when there is no visible plastic melting in the oven--advice?

mossygreen thought this was worth mentioning said

Turned on the oven today and got a two-room-filling melting plastic smell. Turned off the oven after I established there was no more immediate source of melting plastic. Found a little round metal filter-looking thing on the bottom of the oven, which looks like it may have been blocking a hole at the top of the oven. Left oven door open to dissipate smell, turned off power to oven. Not sure what next step is, other than not using oven in the near future. We probably don’t want to replace the oven if we don’t have to, as we will be moving… eventually… somewhere… maybe this summer, maybe in the fall. Possibly even the winter. Don’t want to burn the house down in the meantime, either. Is there any way I can figure this out myself? I’m assuming not, but it never hurts to ask strangers on the internet.