[Xperia Z5 General] millicent:
This is a logcat main buffer log from INFO onwards, I logged these line every time I had any kind of freeze: of course I missed some lines and especially didn't put down single 'underrun' lines (occurring only one at a time) that didn't seem to impact that much, ie no freezing/stuttering I could easily tell. More 'underrun' lines, the bigger the gap/freeze. Sometimes I tried to trigger the problem by turning the screen on, etc. As you can see, the issue happens fairly often, at least once in 5 minutes.

I intend to create an entry on talk.sonymobile later today where I will resume our collective experience and invite you all to also add your comments over there.

03-16 08:48:15.460 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 08:48:15.470 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 08:48:15.485 9738 10575 W bt_btif : underrun only read 0 bytes out of 240

3-16 08:51:25.852 9738 10575 W bt_btif : underrun only read 192 bytes out of 240
03-16 08:51:25.862 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 08:51:25.872 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 08:51:27.803 9738 9959 W bt_hci_packet_fragmenter: reassemble_and_dispatch complete l2cap packet received:l2cap full length 5 and hci length 13.

03-16 08:57:41.825 9738 10575 W bt_btif : underrun only read 80 bytes out of 240
03-16 08:57:41.835 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 08:57:41.845 9738 10575 W bt_btif : underrun only read 0 bytes out of 224
03-16 08:57:41.856 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 08:57:41.870 9738 10575 W bt_btif : underrun only read 0 bytes out of 240

03-16 09:01:16.880 9738 10575 W bt_btif : underrun only read 176 bytes out of 224
03-16 09:01:16.890 9738 10575 W bt_btif : underrun only read 0 bytes out of 224
03-16 09:01:16.901 9738 10575 W bt_btif : underrun only read 0 bytes out of 240

03-16 09:01:39.080 9738 10575 W bt_btif : underrun only read 32 bytes out of 224

03-16 09:02:37.406 9738 9959 W bt_hci_packet_fragmenter: reassemble_and_dispatch complete l2cap packet received:l2cap full length 5 and hci length 13.
03-16 09:02:38.059 1812 2036 I DisplayManagerService: Display device changed state: "Built-in Screen", OFF
03-16 09:02:40.299 1812 3695 I AccountManagerService: getTypesVisibleToCaller: isPermitted? true
03-16 09:02:40.324 3258 4527 I Icing : Performing maintenance.
03-16 09:02:40.385 9738 10575 W bt_btif : underrun only read 112 bytes out of 240
03-16 09:02:40.395 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 09:02:40.445 1812 3939 E LocSvc_libulp: E/int ulp_brain_transition_all_providers(), no QUIPC/GNSS transition logic run due to both engines are OFF
03-16 09:02:40.483 4704 4704 I GCoreUlr: Starting service, intent=Intent { act=com.google.android.location.reporting.ACTION_UPDATE_ACTIVE_STATE cmp=com.google.android.gms/com.google.android.location.reporting.service.DispatchingService (has extras) }, extras=Bundle[{source=PowerModeReceiver}]
03-16 09:02:40.492 4704 5018 I GCoreUlr: Successfully inserted 1 locations
03-16 09:02:40.494 4704 5018 I GCoreUlr: Cancelling scheduled uploads
03-16 09:02:40.496 4704 5018 I GCoreUlr: Not calling LocationReporter, hasMoved: true, elapsed millis: 298539, request: Moving(600000)
03-16 09:02:40.497 4704 5018 I GCoreUlr: Scheduling next upload for 301461ms from now
03-16 09:02:40.545 4704 5018 I GCoreUlr: DispatchingService.updateActiveState+PowerModeReceiver: Ensuring that reporting is active for [account#8#]
03-16 09:02:40.565 9738 10575 W bt_btif : underrun only read 144 bytes out of 240
03-16 09:02:40.575 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 09:02:40.586 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 09:02:40.590 4704 5018 I GCoreUlr: GMS FLP location and AR updates requested: {"description":"default","newRequest":true,"samplePeriodMs":120000,"sampleReason":"default","sampleSource":"internal","timestampMs":1458133360518}
03-16 09:02:40.596 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 09:02:40.609 4704 5018 I GCoreUlr: Place inference reporting - stopped
03-16 09:02:40.610 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 09:02:40.624 4704 5018 I GCoreUlr: Cancelling scheduled uploads
03-16 09:02:40.625 9738 10575 W bt_btif : underrun only read 0 bytes out of 240
03-16 09:02:40.625 4704 5018 I GCoreUlr: Not calling LocationReporter, hasMoved: true, elapsed millis: 298669, request: Moving(600000)
03-16 09:02:40.625 4704 5018 I GCoreUlr: Scheduling next upload for 301331ms from now