Instability at Joints

Good day, I would like ask for some advice regarding this structure and its instabilities at joints 6 and 27. How should I go about rectifying this. And will it affect the design?

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 14-Jun-16
END JOB INFORMATION
INPUT WIDTH 79
UNIT MMS KN
JOINT COORDINATES
1 0 0 0; 2 4000 0 0; 3 0 2560 0; 4 4000 2560 0; 5 200 2560 200;
6 200 2560 -200; 7 -200 2560 200; 8 -200 2560 -200; 26 4200 2560 200;
27 4200 2560 -200; 28 3800 2560 200; 29 3800 2560 -200; 30 -570 2560 0;
31 4570 2560 0; 32 0 2560 400; 33 0 2560 -400; 34 4000 2560 400;
35 4000 2560 -400;
MEMBER INCIDENCES
2 1 3; 3 2 4; 73 30 3; 74 3 4; 75 4 31; 76 33 3; 77 3 32; 78 35 4; 79 4 34;
ELEMENT INCIDENCES SHELL
80 8 3 7; 81 3 5 7; 82 3 6 5; 83 6 3 8; 84 29 4 28; 85 4 26 28; 86 4 27 26;
87 27 4 29;
ELEMENT PROPERTY
80 TO 87 THICKNESS 16
DEFINE MATERIAL START
ISOTROPIC STEEL
E 205
POISSON 0.3
DENSITY 7.68195e-008
ALPHA 1.2e-005
DAMP 0.03
TYPE STEEL
STRENGTH FY 0.2532 FU 0.4078 RY 1.5 RT 1.2
END DEFINE MATERIAL
MEMBER PROPERTY AMERICAN
2 3 TABLE ST HSSP8.625X0.188
76 TO 79 TABLE D C4X7 SP 247
73 TO 75 TABLE D C4X7 SP 587
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 2 PINNED
MEMBER OFFSET
76 START 0 58.8 0
76 END 0 58.8 0
77 START 0 58.8 0
77 END 0 58.8 0
78 START 0 58.8 0
78 END 0 58.8 0
79 START 0 58.8 0
79 END 0 58.8 0
73 START 0 160.4 0
73 END 0 160.4 0
74 START 0 160.4 0
74 END 0 160.4 0
75 START 0 160.4 0
75 END 0 160.4 0
LOAD 1 LOADTYPE Dead TITLE DEAD
SELFWEIGHT Y -1
MEMBER LOAD
73 CON GY -6.8 120
74 CON GY -6.8 2000
75 CON GY -6.8 450
LOAD 2 LOADTYPE Wind TITLE WIND +X
MEMBER LOAD
2 3 TRAP GX 0 1.37 0 2560
LOAD 3 LOADTYPE Wind TITLE WIND +Z
MEMBER LOAD
2 3 TRAP GZ 0 1.37 0 2560
73 75 UNI GZ 1.37 0 570
74 UNI GZ 1.37 0 4000
LOAD 4 LOADTYPE Wind TITLE WIND +X +Z
MEMBER LOAD
2 3 TRAP GX 0 1.37 0 2560
2 3 TRAP GZ 0 1.37 0 2560
73 75 UNI GZ 1.37 0 570
74 UNI GZ 1.37 0 4000
LOAD 5 LOADTYPE Wind TITLE WIND +X -Z
MEMBER LOAD
2 3 TRAP GX 0 1.37 0 2560
2 3 TRAP GZ 0 -1.37 0 2560
73 75 UNI GZ -1.37 0 570
74 UNI GZ -1.37 0 4000
LOAD 6 LOADTYPE Wind TITLE WIND -X +Z
MEMBER LOAD
2 3 TRAP GX 0 -1.37 0 2560
2 3 TRAP GZ 0 1.37 0 2560
73 75 UNI GZ 1.37 0 570
74 UNI GZ 1.37 0 4000
LOAD 7 LOADTYPE Wind TITLE WIND -X -Z
MEMBER LOAD
2 3 TRAP GX 0 -1.37 0 2560
2 3 TRAP GZ 0 -1.37 0 2560
73 75 UNI GZ -1.37 0 570
74 UNI GZ -1.37 0 4000
LOAD COMB 8 COMBINATION LOAD CASE 8
1 1.2 2 1.6
LOAD COMB 9 COMBINATION LOAD CASE 9
1 1.2 3 1.6
LOAD COMB 10 COMBINATION LOAD CASE 10
1 1.2 4 1.6
LOAD COMB 11 COMBINATION LOAD CASE 11
1 1.2 5 1.6
LOAD COMB 12 COMBINATION LOAD CASE 12
1 1.2 6 1.6
LOAD COMB 13 COMBINATION LOAD CASE 13
1 1.2 7 1.6
PERFORM ANALYSIS
PARAMETER 1
CODE AISC UNIFIED 2010
SELECT OPTIMIZED
CHECK CODE ALL
FINISH

Thank you in advance for all your assistance.