Could this (see report below) be related to a mounted NAS? On Mojave, most times I shut down it would just hang without the "report" and not shutdown unless I force ejecetd the NAS and restarted Finder first. Since Catalina, I get this report mostly after restarting or powering up (but the imac pro doesn't restart during use or at idle, so odd). Either way quite annoying.
anic(cpu 0 caller 0xffffff8013cc31a3): "PowerOff timed out in phase 'Notifying power plane drivers'. Total 30000 ms:
vfs_unmountall: 1551 ms
PowerOff/Restart message to priority client: 11119 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 3329 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 7002 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 7048 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 274 ms @ 0x<ptr>, com.apple.iokit.IOGraphicsFamily(576.1)[B1C0006F-E1F5-37D9-9548-5F918E92B422]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 101 ms @ 0x<ptr>, com.apple.driver.IOBluetoothHIDDriver(7.0.5f6)[875A40E1-49A4-3DDE-A094-5D609CC30D3D]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 174 ms @ 0x<ptr>, com.apple.driver.IOBluetoothHIDDriver(7.0.5f6)[875A40E1-49A4-3DDE-A094-5D609CC30D3D]@0x<ptr>->0x<ptr>
PowerOff/Restart handler completed: 620 ms @ 0x<ptr>, com.apple.iokit.IOUSBHostFamily(1.2)[23C6290C-B42C-3885-B77D-09995CE04183]@0x<ptr>->0x<ptr>
"@/AppleInternal/BuildRoot/Library/Caches/com.apple.xbs/Sources/xnu/xnu-6153.121.1/iokit/Kernel/IOPMrootDomain.cpp:5403
Backtrace (CPU 0), Frame : Return Address
0xffffffa75aa03bc0 : 0xffffff801351f5cd
0xffffffa75aa03c10 : 0xffffff8013658b05
0xffffffa75aa03c50 : 0xffffff801364a68e
0xffffffa75aa03ca0 : 0xffffff80134c5a40
0xffffffa75aa03cc0 : 0xffffff801351ec97
0xffffffa75aa03dc0 : 0xffffff801351f087
0xffffffa75aa03e10 : 0xffffff8013cc27ec
0xffffffa75aa03e80 : 0xffffff8013cc31a3
0xffffffa75aa03ea0 : 0xffffff8013c49fa4
0xffffffa75aa03ec0 : 0xffffff8013561565
0xffffffa75aa03f40 : 0xffffff8013561091
0xffffffa75aa03fa0 : 0xffffff80134c513e
BSD process name corresponding to current thread: kernel_task
anic(cpu 0 caller 0xffffff8013cc31a3): "PowerOff timed out in phase 'Notifying power plane drivers'. Total 30000 ms:
vfs_unmountall: 1551 ms
PowerOff/Restart message to priority client: 11119 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 3329 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 7002 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 7048 ms @ 0x<ptr>, com.apple.iokit.IOStorageFamily(2.1)[E13E9C61-F1F5-3A81-B1EF-65669C3CBDBF]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 274 ms @ 0x<ptr>, com.apple.iokit.IOGraphicsFamily(576.1)[B1C0006F-E1F5-37D9-9548-5F918E92B422]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 101 ms @ 0x<ptr>, com.apple.driver.IOBluetoothHIDDriver(7.0.5f6)[875A40E1-49A4-3DDE-A094-5D609CC30D3D]@0x<ptr>->0x<ptr>
PowerOff/Restart message to priority client: 174 ms @ 0x<ptr>, com.apple.driver.IOBluetoothHIDDriver(7.0.5f6)[875A40E1-49A4-3DDE-A094-5D609CC30D3D]@0x<ptr>->0x<ptr>
PowerOff/Restart handler completed: 620 ms @ 0x<ptr>, com.apple.iokit.IOUSBHostFamily(1.2)[23C6290C-B42C-3885-B77D-09995CE04183]@0x<ptr>->0x<ptr>
"@/AppleInternal/BuildRoot/Library/Caches/com.apple.xbs/Sources/xnu/xnu-6153.121.1/iokit/Kernel/IOPMrootDomain.cpp:5403
Backtrace (CPU 0), Frame : Return Address
0xffffffa75aa03bc0 : 0xffffff801351f5cd
0xffffffa75aa03c10 : 0xffffff8013658b05
0xffffffa75aa03c50 : 0xffffff801364a68e
0xffffffa75aa03ca0 : 0xffffff80134c5a40
0xffffffa75aa03cc0 : 0xffffff801351ec97
0xffffffa75aa03dc0 : 0xffffff801351f087
0xffffffa75aa03e10 : 0xffffff8013cc27ec
0xffffffa75aa03e80 : 0xffffff8013cc31a3
0xffffffa75aa03ea0 : 0xffffff8013c49fa4
0xffffffa75aa03ec0 : 0xffffff8013561565
0xffffffa75aa03f40 : 0xffffff8013561091
0xffffffa75aa03fa0 : 0xffffff80134c513e
BSD process name corresponding to current thread: kernel_task