Well, finnaly I got an explanation from Ec guys. VEH PARAM OVERLIMIT is suppose to be a message warning the crew, that one of the parameters has been in the caution area - in our case MM was in yellow at one time not exceeding 7,5'' (manitenance acknowledged) - and so you don't have the safety factor of reaching that level of exceedence once again without manitenance action taken - expensive.
Funny that EC manuals don't say much about it.