I have released the fix mentioned above by Ralkage as version 0.1.4 while we wait for the other changes to be completed.
To update and fix the ReflectionException issue:
composer update fof/frontpage
Additional notes: it seems this issue was only happening while using the optimized class loader of Composer, which is what Flarum uses during update steps with the -a
flag to Composer's update
/require