error when using closeloop

I ran into questions when I use closeloop to make prediction. I search around the related previous questions which help me understand NARX more, but I still haven't get things figured out. Here is my problem, the code I use is as follows:

net = narxnet(1:3,1:3,10);

[x,xi,ai,t] = preparets(net,L,{},P);

net2 = train(net,x,t,xi,ai);

[y1,xf,af] = net2(x,xi,ai);

[netc,xi,ai] = closeloop(net2,xf,af);

[y2,xf,af] = netc(L1,xi,ai);

the data is in the attachment.

I always get the errors like when run the command closeloop,

Error using mat2cell (line 107) Input arguments, D1 through D2, must sum to each dimension of the input matrix size, [1 1].'

Error in nnet7.process_fcn (line 26) if (wasCell), out1 = mat2cell(out1,ii,jj); end

Error in removeconstantrows (line 41) y = nnet7.process_fcn(mfilename,x,varargin{:});

Error in closeloop (line 182) ai = feval(fcn,'apply',ai,settings);

One interesting thing I found is that the error is depend on the contents of dataset P, if I change some value of this, sometimes the error won't show up. What is the reasons for this?Thanks so much in advance for looking into this problem.