Sleep-drain with SMC.OutboxNotEmpty smc.70070000 USB-C_plug

For the last maybe two weeks I noticed that my 14" MacBook Pro M1 Max's battery was almost to totally depleted every morning when I left it to sleep fully charged the evening before (i.e. lid closed, nothing connected by wire or wirelessly, keyboard/mouse switched off).

One morning last week I had put it in my backpack the night before so I was ready to leave but found the backpack quite hot and the battery dead.

Like last night:

You can see the screen has been off but the battery went down constantly and quite rapidly.

After uninstalling everything I've installed in the last month, I still have no change in behaviour.

Delving further into pmlog, I find wakeups for 5-6 seconds every 5-10 seconds all night:

{7:58}~ ➭   pmset -g log | grep -i "wake from" | tail -10
2022-06-24 07:31:18 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 9 secs
2022-06-24 07:31:29 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 5 secs
2022-06-24 07:31:36 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 6 secs
2022-06-24 07:31:44 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 5 secs
2022-06-24 07:31:51 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 6 secs
2022-06-24 07:31:59 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 5 secs
2022-06-24 07:32:06 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 5 secs
2022-06-24 07:32:14 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 5 secs
2022-06-24 07:32:21 +0200 DarkWake            	DarkWake from Deep Idle [CDNP] : due to SMC.OutboxNotEmpty smc.70070000 USB-C_plug/ Using BATT (Charge:14%) 5 secs

Additionally dmesg shows tons of these:

[37468.547636]: IOAccessoryManagerUSBC::setPinConfiguration(): Updating pin configuration...
[37468.547643]: IOAccessoryManagerUSBC::setCableActive(): activeCable: NO
[37468.547647]: IOAccessoryManagerUSBC::setCableOptical(): opticalCable: NO
[37468.547650]: IOAccessoryManagerUSBC::setDisplayPortPinAssignment(): dpPinAssignment: 0
[37468.547654]: IOAccessoryManagerUSBC::setPlugOrientation(): plugOrientation: 0
[37468.547664]: IOPort::messageClients(): [Port-USB-C@1] Messaging clients... (messageType: 0xe3ff8018)

[37468.547732]: IOPort::messageClients(): [Port-USB-C@1] Messaging clients... (messageType: 0xe3ff8013)

[37468.547739]: IOAccessoryTRM::_processNotifications(): Processing notifications...
[37468.547746]: IOAccessoryTRM::_processNotifications(): Thread call scheduled!
[37468.547756]: IOAccessoryTRM::_handleNotifications(): Handling notifications...
[37468.547764]: IOAccessoryTRM::_handleNotifications(): Handling notification... (notificationType: 3) (m_mgrPrimaryPortID: 1)
[37468.549452]: IOAccessoryTRM::_handleNotificationGated(): Handling notification (gated)... (notificationType: 3) (m_mgrPrimaryPortID: 1)
[37468.549460]: IOAccessoryTRM::_handleNotificationGated(): Handling Attach/Detach/AccessoryDetected/ConfigChange/USBConnectChange notification... (m_mgrPrimaryPortID: 1)
[37468.549466]: IOAccessoryTRM::_handleNotificationGated(): supervisedAccessoryAttached: NO, m_status.supervisedAccessoryAttached: NO (m_mgrPrimaryPortID: 1)
[37468.569780]: postMessageInternal:isPipeOpened:0, msg 153, dataLen 56
[37468.569799]: postMessageInternal:isPipeOpened:0, msg 153, dataLen 56
[37468.569804]: postMessageInternal:isPipeOpened:0, msg 153, dataLen 56
[37468.569808]: postMessageInternal:isPipeOpened:0, msg 153, dataLen 56
[37468.582101]: [SPI][HIDSPI]

I know there've been similar issues where disabling wake on lan, BT, iMessage and the like made a change, but in my case I assume it's hardware related, as it's constantly raving about something USB-C related.

Oh, and BetterTouchTool also complained that some USB-device was constantly connecting/disconnecting, which might cause trouble.

Has anyone ever seen anything like this before?

I've already booked a call with Apple as I am well under warranty and also have Apple Care, but I value the power of the many, maybe someone from the community can enlighten me ;)