Ok teste dit on 0.86.2 version
13:24:08.088: N16 G28 X0
13:24:09.526: X:0.00 Y:0.00 Z:0.000 E:0.0000
13:24:09.899: N17 G28 Y0
13:24:10.301: N18 M117 IP:192.168.0.179
13:24:10.673: X:0.00 Y:245.00 Z:0.000 E:0.0000
13:24:18.204: N19 G1 X10.00 F6000
13:24:20.004: N20 G1 X20.00 F6000
13:24:21.636: N21 G1 X30.00 F6000
13:24:22.861: N22 G1 X40.00 F6000
13:24:23.788: N23 G1 X50.00 F6000
13:24:24.967: N24 G1 X60.00 F6000
13:24:26.317: N25 G1 X50.00 F6000
As you see server sends absolute coordinates and increments them as required.
If I set printer to relative coordinates it just always sends 10, but head moves:
13:27:14.097: N39 G28 X0
13:27:16.888: X:0.00 Y:245.00 Z:0.000 E:0.0000
13:27:17.251: N40 G91
13:27:19.976: N41 G1 X10.00 F6000
13:27:20.676: N42 G1 X10.00 F6000
13:27:21.262: N43 G1 X10.00 F6000
13:27:21.821: N44 G1 X10.00 F6000
So if server always sends X10 it thinks printer is in relative mode while it is in absolute mode. Please try sending G90 to convince it that it is in absolute mode. Question is of course still why would server think that. Did you switch outside server so he did not know?