The electric motor in my lawnmower seems to be jammed. Is there a way to access the motor to clear it?

The mower could probably be disassembled, but you may risk voiding your warranty. For an issue like this I would contact Ego directly for advice on how to proceed:

http://egopowerplus.com/pages/contact-us

Phil, we also replied to your email but didn't hear back and we want to make sure you've been taken care of.   It definitely seems like something is caught in your mower and yes, that would be covered under warranty.  Our nearest service centers look to be very far from your location however.  We do have a customer service team that would be happy to help you with a replacement and further troubleshooting.  Please give us a call at 1-855-346-5656 and we'll help you.  We are available Monday through Friday from 8:30AM - 8:00PM EST (Saturday and Sunday from 10:00AM - 6:00PM EST).  There's no real good way to get better access to your mower other than the underside of your deck, which we assume you've already accessed.  Your mower is covered by a 5 year warranty so you can rest easy knowing you're covered.  We look forward to hearing from you.