It unfortunately sounds like it will have to go back to JVC. Last week my remote sensor on front of RS40 quit working but the sensor worked on the back of the projector. I thought I was going to have to send to JVC but after watching a movie and powering down, I unplugged it and next day both sensors worked. Sounds your problem is something more going on. I would contact JVC and since you just got it back from them I would tell them they obviously didn't fix it and you don't feel you should have to pay to have it shipped back. Maybe they can have UPS/FedEx come pick it up on their dime.
JVC RS600(Calibrated with Chromapure using an iD3), Stewart Cima Neve 2.35 115" diagonal screen, Lumagen Radiance XD, Darbee Darblet, Denon AVR-X7200WA(7.6.4), M&K Speakers, 6 ported 18" subs powered by 3 inuke 6000dsps, Roku 4, Panasonic UB-900 UHD blu-Ray player, HDFury