Multi state cooperative societies act 2002

I am a member of a cooperative society registered under the provisions of multi state cooperative societies act 2002. Elections of the Board of Directors was held in the year 2017. Thereafter in the year 2018 out of 9 elected directors 6 resigned from the post of director. There are 3 government nominated directors on the Board of Directors of the Society. Presently remaining Three elected directors and three government nominated directors are on the BOD. Government nominated directors hardly attend board meetings. Bye laws of the society states that "any casual vacancy occurring after the elections of Directors shall be filled up by co-opting on the of the elected delegates. Directors so co-opted shall hold office until the next general body meeting in which the vacancy will be filled up by election." Casual vacancies occurring due to the resignation by 6 directors have not been filled up and the remaining 3 directors are holding the board meeting and taking policy decisions. i want to know as to whether filling up of casual vacancies are mandatory or not and whether the remaining 3 directors can hold board meetings.