HI Alfonso,

Just to let you know that I entered the lines as you suggested in CONN (18a) (conn_process.m):
try, [Q,D]=svd(c1);
catch, [Q,D]=svds(c1,NdimsOut) instead of [Q,D]=svd(c1)

I tested MVPA with MATLAB 2018a with 5 subjects (task, 4 sessions, 2 conditions). It runs smoothly with no errors after 1st level and the results of the second level as expected (tested previously with CONN).

Thank you!

best wishes, 
alla