Interesting one. I installed all this on my Solo as well and I am seeing the same. But checking EVERY button on the virtual remote shows that none of them are allocated to Custom 15, so it looks as though the Android App designer has made a mistake.
Hopefully the Moderators will be reporting this as it is a genuine bug. In the meantime I can probably help out by building you a 'tweaked' Custom Remote and map the function you want onto Custom 15. Which is the button on the PC virtual remote that you use ? The List ?