Hi Tijl.
You have over 2700 items to sync. The system cannot get it done fast enough, so Google eventually times out the request. This is a huge problem with syncing that I need to fix.
Since you have started to use paper temporarily, this might be a good time to remove FocusPad in order to clear out the data, and then re-install it and re-enter your tasks. You will also have to go to the web app and issue this URL to clear out the data there.
[WARNING TO OTHER USERS: this URL will remove all of your data from the web app.]
If this is not acceptable or is too depressing to contemplate, I can work with you to get the data over to the web site so future syncs go more quickly. Or perhaps I can help you prune old tasks.
..tony..