I have Trainz Plus, build 105100. As I mentioned above I have 16 Content-Packs, which can not be updated by the Trainz Content Store.
Thank you very much HPL for the link to the workaround by N3V.
I tried to uninstall one of the packs, sc492 ETR 1000 Frecciarossa, with the uninstall-button in the Trainz Content Store. After working for several hours, I have around 1.7 TB of content in my content folder, the pack was uninstalled and in the Trainz Content Store appeared the button "Install". I installed the pack successfully with this button. After the installation there was no longer the button "Update" but "Uninstall". The train was running, as far as I can say, flawlessly after the re-installation.
I think the other 15 packs I will replace with the workaround by N3V, that should be much faster.
Regards
Swordfish