When I ran that code, I got:

Operands to the || and && operators must be convertible to logical scalar values.

Error in dlmwrite (line 133)
useVectorized = realdata && precnIsNumeric && ~contains('%\',dlm) ...

And below is my P structure (attached file as well):

spmdir=fullfile(maindir,strcat('ALC_',subj{a},'_Onset_Model_withError'));
cd (spmdir);

% set up all parameters
P.equalroi=0; % this allows unequal sized VOIs
P.FLmask=1; % This allows VOIs to be trimmed by the 1st level mask
P.subject=char(subj{a}); % subject number
P.directory=pwd;
P.VOI=fullfile('/mnt/data/GNG_reward/ROIs/striatum/',sprintf('%s.nii',VOI{b}));
P.Region=VOI{b};
P.Estimate=1; % 1 means estimate PPI design
P.contrast=0;
P.extract='eig'; % extract eigenvariate
P.Tasks={'0' 'GS_control' 'NGS_control' ...
'GS_dollar' 'NGS_dollar' ...
'GS_5cent' 'NGS_5cent'}; % All events
P.Weights=[];
P.analysis='psy';
P.method='cond';
P.CompContrasts=1;
P.Weighted=0;
P.outdir=fullfile('/mnt/data/GNG_reward/gPPI/PPI_analysis/',subj{a},filesep);
P.GroupDir=fullfile('/mnt/data/GNG_reward/gPPI/Con_files/',subj{a},VOI{b},filesep);
% Contrast setup
P.Contrasts(1).left={'GS_5cent'};
P.Contrasts(1).right={'GS_control'};
P.Contrasts(1).STAT='T';
P.Contrasts(1).Weighted=0;
P.Contrasts(1).MinEvents=2;
P.Contrasts(1).name='GS_5cent_minus_GS_control';