I have also experienced a similar problem with MCUXpresso IDE v10.3.0 build 2200 while using the GUI Flash Tool. After a successful flash, the next attempt gives the error "XPSR register failed - rc Ep(08). Cannot access core regs when target running. Here is the console output.
Executing flash operation 'Program' (Program file into flash: test.bin) - Tue Feb 19 13:47:48 PST 2019
Checking MCU info...
Scanning for targets...
Executing flash action...
MCUXpresso IDE RedlinkMulti Driver v10.3 (Nov 28 2018 02:33:57 - crt_emu_cm_redlink.exe build 748)
( 0) Reading remote configuration
Wc(03). No cache support.
Found chip XML file in D:/ARM/projects/test/Debug\LPC54608J512.xml
( 5) Remote configuration complete
Reconnected to existing link server
Connecting to probe 1 core 0 (using server started externally) gave 'OK'
Probe Firmware: LPC-LINK2 CMSIS-DAP V5.173 (NXP Semiconductors)
Serial Number: FTATBQBR
VID:PID: 1FC9:0090
USB Path: \\?\hid#vid_1fc9&pid_0090&mi_00#11&28d209ff&0&0000#{4d1e55b2-f16f-11cf-88cb-001111000030}
Using memory from core 0 after searching for a good core
( 30) Emulator Connected
( 40) Debug Halt
( 50) CPU ID
debug interface type = Cortex-M3/4 (DAP DP ID 2BA01477) over SWD TAP 0
processor type = Cortex-M4 (CPU ID 00000C24) on DAP AP 0
number of h/w breakpoints = 6
number of flash patches = 2
number of h/w watchpoints = 4
Probe(0): Connected&Reset. DpID: 2BA01477. CpuID: 00000C24. Info: <None>
Debug protocol: SWD. RTCK: Disabled. Vector catch: Disabled.
Content of CoreSight Debug ROM(s):
RBASE E00FF000: CID B105100D PID 04000BB4C4 ROM (type 0x1)
ROM 1 E000E000: CID B105E00D PID 04000BB00C Gen SCS (type 0x0)
ROM 1 E0001000: CID B105E00D PID 04003BB002 Gen DWT (type 0x0)
ROM 1 E0002000: CID B105E00D PID 04002BB003 Gen FPB (type 0x0)
ROM 1 E0000000: CID B105E00D PID 04003BB001 Gen ITM (type 0x0)
ROM 1 E0040000: CID B105900D PID 04000BB9A1 CSt TPIU type 0x11 Trace Sink - TPIU
ROM 1 E0041000: CID B105900D PID 04000BB925 CSt ETM type 0x13 Trace Source - Core
NXP: LPC54608J512
DAP stride is 4096 bytes (1024 words)
Inspected v.2 On-chip Flash Memory LPC5460x_512K.cfx
Image 'LPC5460x (512K Flash) Aug 23 2017 12:13:28'
Inspected v.2 External Flash Device on SPI LPC5460x_SPIFI_GENERIC.cfx
Image 'LPC5460x Generic SPIFI Sep 25 2017 16:15:07'
Opening flash driver LPC5460x_SPIFI_GENERIC.cfx
Sending VECTRESET to run flash driver
Flash variant 'MT25QL128AB' detected (16MB = 256*64K at 0x10000000)
Closing flash driver LPC5460x_SPIFI_GENERIC.cfx
( 65) Chip Setup Complete
Connected: was_reset=false. was_stopped=false
( 70) License Check Complete
Loading 'test.bin' Binary 0x00000000 len 0x10000
Opening flash driver LPC5460x_512K.cfx
Sending VECTRESET to run flash driver
XPSR register failed - rc Ep(08). Cannot access core regs when target running.
(100) Writing Flash ended with an error.
File 'test.bin' load failure: Ep(08). Cannot access core regs when target running.
(100) Target Connection Failed
Unable to perform operation!
Command failed with exit code 1
The problem is fixed by pressing the 'Clean Up Debug' button or cycling power to the LPCXpresso54608 development board. I think this problem only started occurring recently. It used to take many flashes before this error shows up. Now, it occurs every other time.