Yet another question about local time signatures

I'm working on typing out the full score for Respighi's Concerto in Modo Misolidio. In mm. 234-243, the LH of the piano is supposed to be in 9/4, while everything else is in 3/2. I wasn't familiar with MuseScore before I started this project so I didn't block in the local time signatures before starting to input notes. As expected, MuseScore won't let me make a local time signature there now due to the classic "measure is nonempty". I've read https://musescore.org/en/node/254556 a handful of times and I understand that basically the only thing to do is delete the measures and put in new ones. No big loss since this range is in the cadenza so the rest of the instruments don't have anything anyways.

Issue: even when I delete the range and put in new measures, it still tells me the range is nonempty.

In this particular case, it's not the end of the world if it just can't be done; I'm totally fine with leaving the LH in 3/2, changing it to display as 9/4 through the "time signature properties" menu, and writing the LH with hidden tuplets. The reason I want to understand what's going on here is that it's a simple version of a more complicated issue elsewhere in the piece: In m. 144 all instruments are in 3/2, but in mm. 145-164 they start changing over to 9/4 in different places. This section I did block in before inputting any notes, but I made some mistakes with the time signatures, and only realized it after entering all the string parts. Assuming that it would be receptive to my attempt, I would like to delete that range and re-type it properly. But I don't want to spend any time wrestling with it if its going to present the same problem as the mm. 234-243 range.

I've attached what I have so far. Thanks in advance for any help.