Hi all When unscrewing the filter ring to add a ND filter on my new Phantom 4, I noticed that the threads was very gritty and not running smoothly like on a normal DSLR lens filter. I added the ND filer and started to screw the filter ring back on, making sure the threads aligned correctly. Same gritty feeling when screwing the filter ring back on, although I checked the threads for any prarticles or aluminium dust. About 2/3 in the filter ring just jammed completely. Have tried every suggestion google and youtube have come up with to unscrew the filter ring again... rubber band, jar opener, heat... but I suspect that the threads are torn. Now I'm stuck with a ND filter that does not come off! Any idea on what to do next?