Hi and thanks for your answer.
Yes I'm running on v wheels.
The Y-axis is a C-Beam linaer rail (https://openbuildspartstore.com/c-beam-linear-rail/) with this plate: https://openbuildspartstore.com/c-beam-gantry-plate-xlarge/.

With disconnected belt it starts moving when I tilt the printer only a little bit and I can move it easily very fast.

17:48:29 M913
Motor current % of normal - X:100, Y:100, Z:100, E:100
17:48:20 M906
Motor current (mA) - X:1000, Y:1000, Z:1000, E:1100, idle factor 30%

I today watched the printer a little bit more and the printer went loud sometimes when doing fast direction changes (resonace vibrations?), but did not have layer shifts. But I think that could cause layer shifts?
But I'm really sure it did not happen when I watched the print yesterday. It wasn't louder than normal and I couldn't see something special. And suddently there was a layer shift.

For the beginning, I will reduce acceleration and observe the problem.

Hi there,

I'm using duet wifi since 1 year and I really like it.
I have a printer originally based on a Anet A8, but completly redone with v-rails and so on...

In the last year I was printing with the same settings like now for months and had never problems with layer shifts. In the sommer months I stopped printing due to high temperatures in my room and I started printing again 2 weeks ago.

After some prints without problems ( I was looking to new versions and updated from v1.20 to v2.02RC2.:
Firmware Name: RepRapFirmware for Duet 2 WiFi/Ethernet
Firmware Electronics: Duet WiFi 1.02 or later
Firmware Version: 2.02RC2(RTOS) (2018-09-07b2)
WiFi Server Version: 1.21
Web Interface Version: 1.22.3

Since then I really struggle with layer shifts... Sometimes I have many layer shifts (about 0.3-0.5mm per shift) in one print. I printed one part 4 times with the same G-code. 3 times it had layer shifts at the same position, 1 time it was OK.
The shifts are on my y-axis (heatpad) and seem to be always in the same direction.
I already reduces jerk (half of the value before) and reduced acceleration a bit (still at 4000mm/min), but it did not help.

Here my current movement settings.
M906 X1000 Y1000 Z1000 E1100 ; Set motor currents (mA)
M201 X4000 Y4000 Z100 E6000 ; Accelerations (mm/s^2)
M203 X15000 Y15000 Z1000 E10000 ; Maximum speeds (mm/min)
M566 X350 Y250 Z60 E600 ; Maximum jerk speeds mm/minute

I can imagine, that my acceleration is to much to move my heatbed, but it worked well for months before summer with version v1.20 and below.
I also did not hear, that there were missed steps when the shifts happened.

Do I miss something? Do you have some idea?

Thank you very much,
apo

M122 after a print with at least 3 layer shifts:
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 2.02RC2(RTOS) running on Duet WiFi 1.02 or later
Board ID: 08DDM-9FAM2-LW4SD-6JKFD-3S86N-9MWVX
Used output buffers: 3 of 20 (10 max)
=== RTOS ===
Static ram: 28460
Dynamic ram: 98312 of which 0 recycled
Exception stack ram used: 460
Never used ram: 3840
Tasks: NETWORK(ready,328) HEAT(blocked,1232) MAIN(running,3484)
Owned mutexes:
=== Platform ===
Last reset 03:24:21 ago, cause: power up
Last software reset at 2018-10-10 23:56, reason: User, spinning module GCodes, available RAM 3888 bytes (slot 3)
Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0041f000 BFAR 0xe000ed38 SP 0xffffffff Task 0x4e49414d
Error status: 0
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest block write time: 82.4ms, max retries 0
MCU temperature: min 25.9, current 31.3, max 34.6
Supply voltage: min 23.7, current 24.4, max 24.7, under voltage events: 0, over voltage events: 0
Driver 0: standstill, SG min/max 0/1023
Driver 1: standstill, SG min/max 0/1023
Driver 2: standstill, SG min/max 12/159
Driver 3: standstill, SG min/max 0/152
Driver 4: standstill, SG min/max 0/1023
Date/time: 2018-10-12 01:14:04
Slowest loop: 207.99ms; fastest: 0.06ms
=== Move ===
Hiccups: 0, StepErrors: 0, LaErrors: 0, FreeDm: 240, MinFreeDm: 126, MaxWait: 829011ms, Underruns: 0, 0
Scheduled moves: 0, completed moves: 0
Bed compensation in use: mesh
Bed probe heights: 0.000 0.000 0.000 0.000 0.000
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1
Heater 0 is on, I-accum = 0.3
Heater 1 is on, I-accum = 0.6
=== GCodes ===
Segments left: 0
Stack records: 2 allocated, 0 in use
Movement lock held by null
http is idle in state(s) 0
telnet is idle in state(s) 0
file is idle in state(s) 0
serial is idle in state(s) 0
aux is idle in state(s) 0
daemon is idle in state(s) 0
queue is idle in state(s) 0
autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Slowest loop: 209.62ms; fastest: 0.01ms
Responder states: HTTP(0) HTTP(2) HTTP(0) HTTP(0) FTP(0) Telnet(0) Telnet(0)
HTTP sessions: 1 of 8

• WiFi -
  Network state is running
  WiFi module is connected to access point
  Failed messages: pending 0, notready 0, noresp 0
  WiFi firmware version 1.21
  WiFi MAC address 5c:cf:7f:ee:64:e7
  WiFi Vcc 3.39, reset reason Turned on by main processor
  WiFi flash size 4194304, free heap 13064
  WiFi IP address 192.168.100.95
  WiFi signal strength -64dBm, reconnections 0, sleep mode modem
  Socket states: 4 4 0 0 0 0 0 0
  === Expansion ===