"The session leader intervenes and tries to help the users to isolate particular aspects of the system that may contribute to the system's perceived lack of flexibility."
I googled for perceived definition:
interpret or regard (someone or something) in a particular way
I guess the perceived usage here is trying to describe how people feel about the lack of flexibility. But not quite sure the meaning here. I have seen such kind of usage very often by using perceived in front of a noun.
Please help me with more explanation about the meaning.
Thanks.