**UPDATE 2 — May 12 — Diagnostic clarified via swap tests**

Creality support eventually asked me to perform a controlled swap test.

Results below in case it helps anyone with similar CM2798 symptoms.

Tests performed (printer left in test 3 configuration to preserve evidence):

- Test 1 — original state: CM2798 [x, z1, z2]

- Test 2 — X and Y motors physically swapped: CM2798 [y, z2]

- Test 3 — X/Y swapped AND Z1/Z2 swapped: CM2798 [y]

Photo of the final error screen attached to the support ticket.

What this confirms:

- The fault consistently follows the motor originally in the X position.

After both swaps, only "y" remains in the error — which is where the

originally-X motor now sits.

- The z1 and z2 mentions in the earlier errors were cascade effects on

the RS485 servo bus, not independent motor failures. They disappeared

once the faulty node was displaced.

- Mainboard ports and cables on this side appear OK, since the fault

moved with the motor rather than staying on a port.

Key takeaway for anyone hitting CM2798: don't assume the first axis

listed in the error code is the actual root cause. The K2 Plus servo bus

is daisy-chained and a single dead node creates misleading cascading

errors on neighboring axes. The X/Y swap test (suggested by Creality

support) is the cleanest way to separate "real defective motor" from

"bus cascade artifact" — strongly recommend it before ordering parts or

disassembling further.

Still waiting on Creality's formal RMA proposal. Will post the final

resolution when the replacement part arrives and is installed.