Cold formed sections (BS5950) - Section is subject to torsional or torsional flexural buckling

What the code says:

When designing a section which is subjected to axial load and major axis bending, combined bending and compression checks are required in accordance with section 6.4 of BS5950-5. Under clause 6.4.1 of this section it says that the checks apply to members 'which are not subject to torsional or torsional flexural buckling.' The torsional and torsional flexural buckling capacities ie P_{T} and P_{TF} are calculated in accordance with section 6.3 and then compared to the elastic flexural buckling capacity P_{E} which is min(P_{Ex},P_{Ey}). If P_{T} or P_{TF} is less than P_{E} then the section will fail by either torsional or torsional flexural buckling as opposed to elastic flexural buckling and therefore section 6.4 ie the combined bending and compression check is not valid and so the calculation terminates with the message as stated. 

How to resolve

If the member is restrained about the minor axis then the checkbox for 'Laterally restrained' under 'Ultimate moments about x axis' on the 3rd page of the interface could be checked and then 'Length of member between restraints to y axis' on the 6th page could be set to 0 mm. If this is done the section passes comfortably, about 30% utilisation.