[Sony Xperia XZ1 Compact ROMs, Kernels, Recoveries,] pixelpedant:
Ah, good thought on the logcat front. Here are the errors I'm getting on the fingerprint reader front:

04-15 19:35:54.638 1059 1059 W FingerprintService: client com.android.settings is no longer authenticating
04-15 19:35:54.638 1059 1059 V FingerprintService: Done with client: com.android.settings
04-15 19:35:54.639 1059 1059 V FingerprintService: handleError(client=com.android.settings, error = 5)
04-15 19:35:54.639 1059 1059 V FingerprintService: start pending client com.android.settings
04-15 19:35:54.639 1059 1059 V FingerprintService: starting client AuthenticationClient(com.android.settings), initiatedByClient = false)
04-15 19:35:54.640 667 667 I AOSP FPC HAL (Binder): authenticate: operation_id=0
04-15 19:35:54.641 667 667 E FPC IMP : ION allocation failed
04-15 19:35:54.641 667 667 E FPC IMP : Error sending data to tz
04-15 19:35:54.642 667 667 E AOSP FPC HAL (Binder): authenticate: Error setting auth challenge to 0. r=0xFFFFFFFF
04-15 19:35:54.642 667 667 E AOSP FPC HAL (Binder): An unknown error returned from fingerprint vendor library: -1
04-15 19:35:54.642 1059 1059 W FingerprintService: startAuthentication failed, result=1
04-15 19:35:54.645 667 667 I AOSP FPC HAL (Binder): getAuthenticatorId : ID : 2856917861
04-15 19:35:54.646 1059 1059 V FingerprintService: startAuthentication(com.android.settings)
04-15 19:35:54.646 1059 1059 V FingerprintService: request stop current client com.android.settings
04-15 19:35:54.646 667 667 I AOSP FPC HAL (Binder): cancel : +
04-15 19:35:54.647 667 667 D AOSP FPC HAL (Binder): setState
04-15 19:35:54.647 667 667 W AOSP FPC HAL (Binder): setState : Already running in state = 0
04-15 19:35:54.647 667 667 W AOSP FPC HAL (Binder): cancel : Thread already in idle state
04-15 19:35:54.647 667 667 I AOSP FPC HAL (Binder): isChangeWaiting : RUN STATE : 0 || TARGET STATE : 0
04-15 19:35:54.648 667 667 I AOSP FPC HAL (Binder): isChangeWaiting : Waiting for state machine to update to target state
04-15 19:35:54.648 667 667 I AOSP FPC HAL (Binder): cancel : -
04-15 19:35:54.649 1059 1059 W FingerprintService: client com.android.settings is no longer authenticating
04-15 19:35:54.649 1059 1059 V FingerprintService: Done with client: com.android.settings
04-15 19:35:54.650 1059 1059 V FingerprintService: handleError(client=com.android.settings, error = 5)
04-15 19:35:54.650 1059 1059 V FingerprintService: start pending client com.android.settings
04-15 19:35:54.650 1059 1059 V FingerprintService: starting client AuthenticationClient(com.android.settings), initiatedByClient = false)
04-15 19:35:54.651 667 667 I AOSP FPC HAL (Binder): authenticate: operation_id=0
04-15 19:35:54.652 667 667 E FPC IMP : ION allocation failed
04-15 19:35:54.653 667 667 E FPC IMP : Error sending data to tz
04-15 19:35:54.653 667 667 E AOSP FPC HAL (Binder): authenticate: Error setting auth challenge to 0. r=0xFFFFFFFF
04-15 19:35:54.653 667 667 E AOSP FPC HAL (Binder): An unknown error returned from fingerprint vendor library: -1
04-15 19:35:54.654 1059 1059 W FingerprintService: startAuthentication failed, result=1
04-15 19:35:54.657 667 667 I AOSP FPC HAL (Binder): getAuthenticatorId : ID : 2856917861
04-15 19:35:54.657 1059 1059 V FingerprintService: startAuthentication(com.android.settings)
04-15 19:35:54.657 1059 1059 V FingerprintService: request stop current client com.android.settings
04-15 19:35:54.658 667 667 I AOSP FPC HAL (Binder): cancel : +
04-15 19:35:54.658 667 667 D AOSP FPC HAL (Binder): setState
04-15 19:35:54.659 667 667 W AOSP FPC HAL (Binder): setState : Already running in state = 0
04-15 19:35:54.659 667 667 W AOSP FPC HAL (Binder): cancel : Thread already in idle state
04-15 19:35:54.659 667 667 I AOSP FPC HAL (Binder): isChangeWaiting : RUN STATE : 0 || TARGET STATE : 0
04-15 19:35:54.660 667 667 I AOSP FPC HAL (Binder): isChangeWaiting : Waiting for state machine to update to target state
04-15 19:35:54.660 667 667 I AOSP FPC HAL (Binder): cancel : -
04-15 19:35:54.660 1059 1059 W FingerprintService: client com.android.settings is no longer authenticating
04-15 19:35:54.661 1059 1059 V FingerprintService: Done with client: com.android.settings
04-15 19:35:54.662 1059 1059 V FingerprintService: handleError(client=com.android.settings, error = 5)
04-15 19:35:54.662 1059 1059 V FingerprintService: start pending client com.android.settings
04-15 19:35:54.663 1059 1059 V FingerprintService: starting client AuthenticationClient(com.android.settings), initiatedByClient = false)