"improving bed calibration point" 9 of 9, failed  

"improving bed calibration point" 9 of 9, failed

Hello
I have prusa i3 MK2S FW 3.1.0
I had a problem with the xyz calibration, I solved the 1 phase by tightening Y axis, but now in 2nd phase I have this issue, results from pronterface M45 V2:

echo:busy: processing
Iteration: 1
echo:busy: processing
echo:busy: processing

correction angles: 0.19454, 0.03159
X vector, adjusted: 1.00000, -0.00340
Y vector, adjusted: 0.00055, 1.00000
center, adjusted: 0.25995, 2.71722
echo:busy: processing
Difference after correction:
point #0measured: (114.27500, 0.20250); measured-corrected: (114.25930, 0.33016); target: (114.00000, -2.00000), error: 0.13
point #1measured: (215.11000, 97.92501); measured-corrected: (215.31372, 97.98706); target: (215.00000, 96.00000), error: 0.21
point #2measured: (114.38000, 196.48500); measured-corrected: (114.36736, 196.32981); target: (114.00000, 194.00000), error: 0.16
point #3measured: (12.49000, 98.61500); measured-corrected: (12.31292, 98.67632); target: (12.00000, 96.00000), error: 0.19
echo:busy: processing
echo:busy: processing

echo:busy: processing
echo:busy: processing
echo:busy: processing
correction angles: -0.41625, 0.03224
X vector, adjusted: 1.00003, 0.00727
Y vector, adjusted: 0.00056, 1.00000
center, adjusted: 0.31882, 3.66301
echo:busy: processing
Difference after correction:
point #0measured: (12.64625, 0.25625); measured-corrected: (12.31806, 1.75019); target: (12.00000, -2.00000), error: 1.53
point #1measured: (114.41750, -0.00188); measured-corrected: (114.32118, 2.49123); target: (114.00000, -2.00000), error: 2.49
point #2measured: (214.98123, 0.02687); measured-corrected: (215.32427, 3.22501); target: (215.00000, -2.00000), error: 3.22
point #3measured: (215.01248, 98.01126); measured-corrected: (215.37942, 101.22544); target: (215.00000, 96.00000), error: 3.24
point #4measured: (114.39000, 97.91625); measured-corrected: (114.37633, 100.49166); target: (114.00000, 96.00000), error: 2.58
point #5measured: (12.56750, 98.04250); measured-corrected: (12.37321, 99.75061); target: (12.00000, 96.00000), error: 1.72
point #6measured: (12.61500, 198.70625); measured-corrected: (12.42835, 197.75103); target: (12.00000, 194.00000), error: 0.97
point #7measured: (115.12751, 203.94625); measured-corrected: (114.43148, 198.49208); target: (114.00000, 194.00000), error: 5.50
point #8measured: (214.62500, 202.01626); measured-corrected: (215.43457, 199.22586); target: (215.00000, 194.00000), error: 2.91
Calculation of the machine skew and offset failed.
echo:busy: paused for user
echo:busy: paused for user
Full RX Buffer
echo:enqueing "G80"
echo:Enqueing to the front: "G28 W0"
echo:busy: processing
echo:busy: processing
echo:busy: processing
echo:busy: processing
Undefined bed correction matrix.
Invalid bed correction matrix. Resetting to identity.
Undefined bed correction matrix.
Invalid bed correction matrix. Resetting to identity.
echo:busy: processing

What I see in when table is near 0 in Y axis (close to me if I see in a front view) the sliding of the table is not so smooth, I suppose that is due the angle of the tensor that is now bigger.

I have passed all weekend with trials, but without result..... 🙄 🙄 🙄
thanks in advance...