There are a lot of posts about this issue. I had one as well with my 2015 FJ-09, brought it to the dealer three times and they refused to replace the part, just performed some "cleaning" which lasted a day. Will have to visit another dealer.
I've been using Dowco Guardian Ultralite Plus Motorcycle Cover XL for a year now and really happy with it. Covers the whole bike with top and saddle cases.