ListTemplate cached in Sandboxed process

Sandboxed solution are a great addition to SharePoint 2010 capabilities whenever it is required to deploy own customizations. However, be aware of the restrictions, and some oddities. Today I encountered such an unexpected behaviour. ListTemplates are one of the SharePoint artefacts that allow themselves to be deployed via a Sandboxed solution. In the initial version of a custom ListTemplate, some errors and omissions were made with respect to schema.xml and some forms. I corrected these, and deployed (= uploaded + activated) the Sandboxed solution. To discover next that my changes were not present; not within the Feature-provisioned ListInstance based on the ListTemplate, nor within a manually created FormsLibrary instance based on the custom ListTemplate. It took an AppPool recycle to have the latest deployed ListTemplate definition become effective in the sitecollection. Tip: always recycle the AppPool before re-deploying a Sandboxed solution.