I have an iMac late 2012 with 24GB or RAM and 3 USB disks connected to it, all running time machine in sequence.

After updating to catalina, every time I shutdown the system it takes ages to shutdown and then after reaching the shutdown state, sometimes the screen turns white again, as if it would start again and after a while the screen turns black again with a shutdown message at the middle, in several languages.

Then, if I start the system, I see this crash message:

panic(cpu 1 caller 0xffffff7fa6c96aae): watchdog timeout: no checkins from watchdogd in 184 seconds (97 totalcheckins since monitoring last enabled), shutdown in progress Backtrace (CPU 1), Frame : Return Address 0xffffff82e0b13c40 : 0xffffff802553f98b 0xffffff82e0b13c90 : 0xffffff8025676c15 0xffffff82e0b13cd0 : 0xffffff802566861e 0xffffff82e0b13d20 : 0xffffff80254e6a40 0xffffff82e0b13d40 : 0xffffff802553f077 0xffffff82e0b13e40 : 0xffffff802553f45b 0xffffff82e0b13e90 : 0xffffff8025cd2e05 0xffffff82e0b13f00 : 0xffffff7fa6c96aae 0xffffff82e0b13f10 : 0xffffff7fa6c96472 0xffffff82e0b13f50 : 0xffffff7fa6cabfd6 0xffffff82e0b13fa0 : 0xffffff80254e613e Kernel Extensions in backtrace: com.apple.driver.watchdog(1.0)[58392D62-D9E8-3022-85C1-B78AC93B9167]@0xffffff7fa6c95000->0xffffff7fa6c9dfff com.apple.driver.AppleSMC(3.1.9)[EB9D605D-85B1-3506-8B2E-ABD195817A4F]@0xffffff7fa6c9e000->0xffffff7fa6cbcfff dependency: com.apple.iokit.IOACPIFamily(1.4)[9BA2613C-A129-3EDD-8DC1-2CFF6B62B832]@0xffffff7fa6c8c000 dependency: com.apple.driver.watchdog(1)[58392D62-D9E8-3022-85C1-B78AC93B9167]@0xffffff7fa6c95000 dependency: com.apple.iokit.IOPCIFamily(2.9)[E6E855AD-A5B2-3518-A997-1384B4360708]@0xffffff7fa5f2f000 BSD process name corresponding to current thread: kernel_task Mac OS version: 19A583 Kernel version: Darwin Kernel Version 19.0.0: Wed Sep 25 20:18:50 PDT 2019; root:xnu-6153.11.26~2/RELEASE_X86_64 Kernel UUID: 70EDD61F-8D909B78160 Kernel slide: 0x0000000025200000 Kernel text base: 0xffffff8025400000 __HIB text base: 0xffffff8025300000 System model name: iMac13,2 (Mac-FC02E91DDD3FA6A4) System shutdown begun: YES Panic diags file available: NO (0xe00002cd) System uptime in nanoseconds: 1201012930700 last loaded kext at 692174279981: @filesystems.msdosfs 1.10 (addr 0xffffff7fa9e1c000, size 69632) last unloaded kext at 67316368087: >!AXsanScheme 3 (addr 0xffffff7fa89a7000, size 40960) loaded kexts: com.Cycling74.driver.Soundflower 2 @filesystems.msdosfs 1.10 >!A!BMultitouch 97 >AudioAUUC 1.70 >!AGraphicsDevicePolicy 4.1.46 @AGDCPluginDisplayMetrics 4.1.46 >!AHV 1 |IOUserEthernet 1.0.1 |IO!BSerialManager 7.0.0f8 >AGPM 111.1.18 >!APlatformEnabler 2.7.0d0 >X86PlatformShim 1.0.0 >pmtelemetry 1 >!AUpstreamUserClient 3.6.8 >!AHDAHardwareConfigDriver 283.14 >!AMikeyHIDDriver 131 @Dont_Steal_Mac_OS_X 7.0.0 @GeForce 14.0.0 >!A!IHD4000Graphics 14.0.0 >AGDCBacklightControl 4.1.46 >!AHDA 283.14 >eficheck 1 >!AMikeyDriver 283.14 >ACPI_SMC_PlatformPlugin 1.0.0 >!AThunderboltIP 3.1.3 >!ABacklight 170.18 >!ALPC 3.1 >!ASMCLMU 212 >!AFIVRDriver 4.1.0 >!A!ISlowAdaptiveClocking 4.0.0 >!A!IFramebufferCapri 14.0.0 @nvidia.NVDAStartup 14.0.0 >!AMCCSControl 1.12 @fileutil 20.036.15 @filesystems.autofs 3.0 >!AVirtIO 1.0 @filesystems.hfs.kext 522.0.9 @!AFSCompression.!AFSCompressionTypeDataless 1.0.0d1 @BootCache 40 @!AFSCompression.!AFSCompressionTypeZlib 1.0.0 @filesystems.apfs 1412.11.7 |!ABCM5701Ethernet 10.3.5 @private.KextAudit 1.0 >!ASDXC 1.7.7 >AirPort.Brcm4360 1400.1.1 >!AAHCIPort 341.0.2 >!AACPIButtons 6.1 >!ARTC 2.0 >!AHPET 1.8 >!ASMBIOS 2.1 >!AACPIEC 6.1 >!AAPIC 1.7 >!A!ICPUPowerManagementClient 222.0.0 $!AImage4 1 @nke.applicationfirewall 302 $TMSafetyNet 8 @!ASystemPolicy 2.0.0 >!A!ICPUPowerManagement 222.0.0 |EndpointSecurity 1 >usb.cdc.acm 5.0.0 >usb.serial 6.0.0 >usb.cdc.ecm 5.0.0 >usb.cdc.ncm 5.0.0 >usb.cdc 5.0.0 >!UMergeNub 900.4.2 >!AXsanScheme 3 >!A!BHIDKeyboard 209 >!AHIDKeyboard 209 >IO!BHIDDriver 7.0.0f8 >!AMultitouchDriver 3400.35 >!AInputDeviceSupport 3400.27 >!AGraphicsControl 4.1.46 |IOAVB!F 800.17 >!ASSE 1.0 @nvidia.driver.NVDAGK100Hal 14.0.0 @nvidia.driver.NVDAResman 14.0.0 >DspFuncLib 283.14 @kext.OSvKernDSPLib 529 >IOPlatformPluginLegacy 1.0.0 @!AGPUWrangler 4.1.46 >!ABacklightExpert 1.1.0 |IONDRVSupport 558.3 >!AHDA!C 283.14 |IOHDA!F 283.14 |IOAudio!F 300.2 >!ASMBusPCI 1.0.14d1 >X86PlatformPlugin 1.0.0 >IOPlatformPlugin!F 6.0.0d8 |IOSlowAdaptiveClocking!F 1.0.0 |IOAccelerator!F2 438.1.23 @!AGraphicsDeviceControl 4.1.46 >!AThunderboltEDMSink 4.2.0 >!ASMBus!C 1.0.18d1 |IOGraphics!F 558.3 @plugin.IOgPTPPlugin 800.14 @kext.triggers 1.0 >Core!S 551 |Broadcom!BHost!CUSBTransport 7.0.0f8 |IO!BHost!CUSBTransport 7.0.0f8 |IO!BHost!CTransport 7.0.0f8 |IO!B!F 7.0.0f8 |IO!BPacketLogger 7.0.0f8 >usb.IOUSBHostHIDDevice 1.2 @vecLib.kext 1.2.0 >usb.networking 5.0.0 >usb.!UHostCompositeDevice 1.2 >usb.!UHub 1.2 |IOSerial!F 11 @filesystems.hfs.encodings.kext 1 |IOSurface 269.6 >!AThunderboltDPOutAdapter 6.2.3 >!AThunderboltDPInAdapter 6.2.3 >!AThunderboltDPAdapter!F 6.2.3 >!AThunderboltPCIDownAdapter 2.5.2 >!AThunderboltNHI 5.5.8 |IOThunderbolt!F 7.4.5 |IOEthernetAVB!C 1.1.0 |IOAHCIBlock!S 316.0.5 |IO80211!F 1200.12.2b1 |IOSkywalk!F 1 >mDNSOffloadUserClient 1.0.1b8 >corecapture 1.0.4 |IOAHCI!F 290.0.1 >usb.!UEHCIPCI 1.2 >usb.!UEHCI 1.2 >usb.!UXHCIPCI 1.2 >usb.!UXHCI 1.2 >usb.!UHostPacketFilter 1.0 |IOUSB!F 900.4.2 >!AEFINVRAM 2.1 >!AEFIRuntime 2.1 |IOSMBus!F 1.1 |IOHID!F 2.0.0 $quarantine 4 $sandbox 300.0 @kext.!AMatch 1.0.0d1 >DiskImages 493.0.0 >!AFDEKeyStore 28.30 >!AEffaceable!S 1.0 >!AKeyStore 2 >!UTDM 489.11.2 |IOSCSIBlockCommandsDevice 422.0.2 >!ACredentialManager 1.0 >KernelRelayHost 1 >!ASEPManager 1.0.1 >IOSlaveProcessor 1 |IOUSBMass!SDriver 157.11.2 |IOSCSIArchitectureModel!F 422.0.2 |IO!S!F 2.1 |IOUSBHost!F 1.2 >!UHostMergeProperties 1.2 >usb.!UCommon 1.0 >!ABusPower!C 1.0 |CoreAnalytics!F 1 >!AMobileFileIntegrity 1.0.5 @kext.CoreTrust 1 |IOTimeSync!F 800.14 |IONetworking!F 3.4 |IOReport!F 47 >!AACPIPlatform 6.1 >!ASMC 3.1.9 >watchdog 1 |IOPCI!F 2.9 |IOACPI!F 1.4 @kec.pthread 1 @kec.corecrypto 1.0 @kec.Libm 1 

It calls my attention this line @filesystems.msdosfs... MS DOS FILE SYSTEM???? WTF!

Any ideas?