KDE (Plasma) desktop freezes, but machine remains operable

hm2/hm2_7i76e.0: error finishing read! iter=18471737
hm2/hm2_7i76e.0: error finishing read! iter=18471737

Unexpected realtime delay on task 0 with period 1000000
This Message will only display once per session.
Run the Latency Test and resolve before continuing.
Unexpected realtime delay on task 0 with period 1000000
This Message will only display once per session.
Run the Latency Test and resolve before continuing.

# dmidecode -t 2
# dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 3.1.1 present.

Handle 0x0002, DMI type 2, 15 bytes
Base Board Information
	Manufacturer: Gigabyte Technology Co., Ltd.
	Product Name: Z370N WIFI-CF
	Version: x.x
	Serial Number: Default string
	Asset Tag: Default string
	Features:
		Board is a hosting board
		Board is replaceable
	Location In Chassis: Default string
	Chassis Handle: 0x0003
	Type: Motherboard
	Contained Object Handles: 0

01:00.0 VGA compatible controller: NVIDIA Corporation GK208B [GeForce GT 710] (rev a1) (prog-if 00 [VGA controller])
	Subsystem: Micro-Star International Co., Ltd. [MSI] GK208B [GeForce GT 710]
	Flags: bus master, fast devsel, latency 0, IRQ 136
	Memory at f6000000 (32-bit, non-prefetchable) [size=16M]
	Memory at e8000000 (64-bit, prefetchable) [size=128M]
	Memory at f0000000 (64-bit, prefetchable) [size=32M]
	I/O ports at e000 [size=128]
	Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: nouveau
	Kernel modules: nouveau

# smartctl /dev/nvme0 -a
smartctl 6.6 2017-11-05 r4594 [x86_64-linux-4.19.0-12-rt-amd64] (local build)
Copyright (C) 2002-17, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Number:                       Patriot Scorch M2
Serial Number:                      CD8E0787049E92033077
Firmware Version:                   E8FM11.5
PCI Vendor/Subsystem ID:            0x1987
IEEE OUI Identifier:                0x6479a7
Total NVM Capacity:                 128,035,676,160 [128 GB]
Unallocated NVM Capacity:           0
Controller ID:                      0
Number of Namespaces:               1
Namespace 1 Size/Capacity:          128,035,676,160 [128 GB]
Namespace 1 Formatted LBA Size:     512
Namespace 1 IEEE EUI-64:            6479a7 0b74628135
Local Time is:                      Fri Nov 13 21:48:24 2020 PST
Firmware Updates (0x02):            1 Slot
Optional Admin Commands (0x0017):   Security Format Frmw_DL Self_Test
Optional NVM Commands (0x001e):     Wr_Unc DS_Mngmt Wr_Zero Sav/Sel_Feat
Maximum Data Transfer Size:         512 Pages
Warning  Comp. Temp. Threshold:     90 Celsius
Critical Comp. Temp. Threshold:     94 Celsius

Supported Power States
St Op     Max   Active     Idle   RL RT WL WT  Ent_Lat  Ex_Lat
 0 +     3.00W       -        -    0  0  0  0        0       0
 1 +     2.00W       -        -    1  1  1  1        0       0
 2 +     2.00W       -        -    2  2  2  2        0       0
 3 -   0.1000W       -        -    3  3  3  3     1000    1000
 4 -   0.0050W       -        -    4  4  4  4   400000   90000

Supported LBA Sizes (NSID 0x1)
Id Fmt  Data  Metadt  Rel_Perf
 0 +     512       0         1
 1 -    4096       0         0

=== START OF SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

SMART/Health Information (NVMe Log 0x02, NSID 0xffffffff)
Critical Warning:                   0x00
Temperature:                        45 Celsius
Available Spare:                    100%
Available Spare Threshold:          50%
Percentage Used:                    0%
Data Units Read:                    194,187 [99.4 GB]
Data Units Written:                 2,251,423 [1.15 TB]
Host Read Commands:                 4,660,555
Host Write Commands:                5,156,882
Controller Busy Time:               58
Power Cycles:                       99
Power On Hours:                     2,391
Unsafe Shutdowns:                   45
Media and Data Integrity Errors:    0
Error Information Log Entries:      1
Warning  Comp. Temperature Time:    0
Critical Comp. Temperature Time:    0
Temperature Sensor 2:               45 Celsius

Error Information (NVMe Log 0x01, max 16 entries)
Num   ErrCount  SQId   CmdId  Status  PELoc          LBA  NSID    VS
  0          1     0  0x000c  0x021b      -   2147483776     0     -