I have the same issue. Tried many apps, none worked. I'm on stock MTC19X. (also it seems when I have more than 1 fake location app installed, switching between them is funky. Sometimes they don't stick in the Dev option.)
*** I may have found a s...
I can confirm sd_shadows directions worked on 7.5.1 :good:
I just rooted using his info with option 3 (old). (although it took me awhile tinkering with driver installs)...