Sounds risky…I would continue messages to seller and then escalate to ebay.
I also have my first ebay case open, bought a water heater for a campervan, paid £160 and it arrived missing £70 of parts required for both fitting and running of heater. Negotiations getting nowhere, ebay case opened and he offered a refund knowing full well I've bought the bits and fitted the heater to my van which involved cutting a hole in the bodywork and bumper. I'm only asking £40 towards missing bits…if I escalate to ebay and they find in my favour, how do I get the money? I paid direct via paypal, not through ebay checkout, so paypal won't be interested. I'm also worried that if they find in his favour, will I lose the ability to leave neg feedback?