staging (merge) commits prevents staging further (merge) commits

i made a "cascade" of merges (see below). when i stage one, the next ones suddenly have greyed out "submit" buttons instead of the regular "stage" buttons. things return to normal once the first change is integrated.
while this isn't horrible, it's confusing, causes unnecessary integration runs, and increases the probability of additional pointless merges (if the target branch integrates other changes before i resume the process).

the changes are:
https://codereview.qt-project.org/c/qt/qttranslations/+/552243
https://codereview.qt-project.org/c/qt/qttranslations/+/552244
https://codereview.qt-project.org/c/qt/qttranslations/+/552245
https://codereview.qt-project.org/c/qt/qttranslations/+/552246