You may also try this procedure. worked many times for me
1. find the obb folder of the app u r about to uninstall but want the obb to remain
2. rename the folder and type any letter or number in the end.
3. install the apk but dont open the app.
4. rename the obb folder and erase the characters that weren't originally there (the ones you typed earlier in 2)
5. Try the app now

i hope this helped though