In the last weeks i found some pending Microsoft Office 16 downloads that won’t download nor be cancelled.
This is well documented in https://community.ipfire.org/t/update-accelerator-problem/409.
Very interestingly, the same client is requesting these patches using two different URLs, one of which uses the wrong backslash.
2019-12-01 08:21:25  [updxlrator] Processing URL http://officecdn.microsoft.com/pr/492350f6-3a01-4f97-b9c0-c7c6ddf67d60/Office/Data/v32_16.0.12130.20390.cab
2019-12-01 08:21:29  [updxlrator] Processing URL http://officecdn.microsoft.com/pr/492350f6-3a01-4f97-b9c0-c7c6ddf67d60%5COffice%5CData%5Cv32_16.0.12130.20390.cab
Some URL mangler must be converting the backslash to %\5C, and when wget downloads this file, it doesn't mangle the name, and so the file is saved with the "\" when the script is expecting \%5C.
The temporary solution to cleaning these out (since the trash icon doesn't work) is to delete the contents of /var/updatecache/downloads/VENDOR/
proposed patch submitted at https://lists.ipfire.org/pipermail/development/2019-December/006701.html