Tie (slur, legato) much longer than expected

This is probably a well known issue but I haven't found a solution to this. I have modified a copy of this piece * and wanted to change the ties on it, to make it more suitable for cello. I select two notes that are next to each other:

Now I press T for tie, but the resulting tie goes over several bars instead of the two selected notes.

What is happening there and how can I fix this? The problem of course must come from the original muse score file I downloaded and edited, as this problem does not occur, when I write the staff from scratch. It is very annoying issue for me and I have noticed this in several other scores (that I downloaded) aswell.

Thanks in advance.

Musescore 4.1.1

• https://musescore.com/user/9292486/scores/2086136