# Computationally singular error using MIRT package

We've got a 524*40 data frame of responses to a likert-type scale questionnaire (7 response categories on 40 items). We want to do exploratory multidimensional IRT using the MHRM method to identify the latent structure. When we run

mirt(SAQdata3, 4, method = 'MHRM')


we get the following error message:

Stage 1: Cycle = 1, Log-Lik = -46764.0, Max Change = 0.2500
Stage 1: Cycle = 2, Log-Lik = -45091.4, Max Change = 0.2500