[Fire HD 8 and HD 10 General] Llamos:
Yeah, logcat is confirming that Amazon is doing some weird stuff to contacts (and also confirming why Google Inbox isn't working properly), first off I'm seeing this spammed into logcat a lot when I open Google's Contacts app:

10-12 01:56:17.127 576 2243 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.147 576 948 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.231 576 2215 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.250 576 2055 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.258 576 1324 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.275 576 1362 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.288 576 2231 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.297 576 736 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.307 576 586 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.317 576 2241 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.326 576 2240 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.337 576 1323 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.346 576 948 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.355 576 2229 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.364 576 949 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.379 576 1362 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.388 576 2231 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.396 576 736 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.405 576 586 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists
10-12 01:56:17.418 576 2241 W AccountManagerService: insertAccountIntoDatabase: Account {name=default_account, type=amazon.account}, skipping since the account already exists

When I closed the sign in window for the app though, it showed that I was signed in to Google and let me view my contacts. I think that has to do with me adding that account to the Amazon Contacts app. It doesn't recognize it properly as a Google account, but it will show and manage contacts as if it is some other third party account added to the system. Hope that info helps you out!

Also, Google Inbox is calling on a function of Google's central libraries that requires system app access to execute properly, so it can't load access the web API securely, and crashes. Error down below:

10-12 01:47:52.173 21774 21796 E AndroidRuntime: FATAL EXCEPTION: RequestQueue Command Executor-0
10-12 01:47:52.173 21774 21796 E AndroidRuntime: Process: com.google.android.apps.inbox, PID: 21774
10-12 01:47:52.173 21774 21796 E AndroidRuntime: dgb: java.lang.SecurityException: Invalid value for is_public_api: true
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at dfx.a(PG:37)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at dfp.run(PG:48)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at java.lang.Thread.run(Thread.java:761)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: Caused by: java.lang.SecurityException: Invalid value for is_public_api: true
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at android.os.Parcel.readException(Parcel.java:1686)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:183)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at android.content.ContentProviderProxy.insert(ContentProviderNative.java:476)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at android.content.ContentResolver.insert(ContentResolver.java:1276)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: at dfx.a(PG:30)
10-12 01:47:52.173 21774 21796 E AndroidRuntime: ... 4 more

I love that Launcher Hijack 2.1 works, though :) That's a lifesaver!