Parallels Desktop 26.2.0 (57363) unable to update Parallels Tools in macOS 10.9.5 Mavericks

I am using Parallels Desktop on an Intel Mac Pro 2019 (16-core, 96 GB RAM) to run a virtual reaaally old macOS 10.9.5 Mavericks - because I need to occasionally use software from this time and age. The host OS is Sequoia 15.7.3.
After the recent update to Parallel Desktop 26.2.0, the update of Parallels Tools in my virtualized old macOS Mavericks fails. If I initiate it via the icon or the menu, the prompt to install it will appear, followed by a progress bar that remains at 0%. After a couple of seconds, the window with the progress bar disappears - obviously without actually updating Parallels tools.
I do have some issues with occasionally stuck key repeats and upper/lower case mixups, so I think an update of the Parallels Tools might be worthwhile. But the according installation just stalls.
Can anyone confirm this, or, even better, suggest a solution? Many thanks in advance!