Theres always crossover. You work as part of a team to create solutions to things. Not every designer will specialize in mechanical or electrical design, but it’s pretty frequent that you will have to sit with the ME and say “no this part should look like this” and start sketching through details like draft, cross sections, wall thicknesses etc.
If they are asking you to work more on something that can turn into a product, either step into the responsibility (they clearly seem to think you are capable) or say “I’m sorry boss I can’t handle this, but I think we should hire an Industrial Designer who can specialize in this area”.