Parallel Computing Got Error Unexpected Standard exception from MEX file what () is: bad allocation

I have 12 workers on my parallel pool. Here is my code 'ptest.m':

M = 30;
accuracy = zeros(1,M);
parfor i = 1:M 
  TreeStruct = TreeBagger(100,train_data,train_label);
  test_label_predict = str2num(cell2mat(predict(B,test_data)));
  accuracy(i) = sum(test_label_predict == test_label)/length(test_label)*100;
end

then I ran it with

job = batch('ptest','Pool',10);

I got an error from workers:

Unexpected Standard exception from MEX file.
What() is:bad allocation

I change M = 10, it works.

for M = 3 * No.Workers, this works from 1 to 7 (No.Workers).

If I change the No.Trees to 50 in TreeBagger function, it also works.

Does this mean that workers have some limited memory or what?

And how can I fix this problem?

Thanks in Advance~!