Measure split option greyed out

I created a score with four instrument, generate the parts for each one;
From the main sheet, copy the entire pease and add measure at the end and paced it at the end. Then made some correction to what was added and notice that the pickup measure was not apply so try to select the notes, when to tool measure and split, it could not split the measure because all the option on the measure under tool are grid out.
I try inserting one mesure after the pickup measure and selecting the rest and try to split it still grid out. It sense the application blocked the measure option, no matter what i do it will not allow to split.

I can add the file be case now I’m on the iPad working on something else. So I don’t have it handy to share it, sorry.

Work around:
Export it to xml file.
Install back MuseScore 2.xx
Open it there, the option was enable, split and made all correction.

I guess the program is set to block split or join under certain circumstances, and remain block (grid out) for good.
There should be a way to unblock the option to continue editing the score.