cannot correct shift in time

if you import a pdf to use as a basis of an arrangement o if you like to modify a piece it happens that the time is shifted in time.
f.i. a pause is missing so the rest of the partiture is all shifted of one beat.
In order to correct it it is necessary to rewrite all because it is not possible to insert a pause
in my attached example we have imported msc1 and abtained msc2
all the rest of the partiture is shifted of 1/8 .... then at a certain point there is one more shift and so on

it could be simple to correct inserting 1/8 pause and having all the rest of the partiture shifted
but it seems it is not possible