Due to a bug in H5P, you may see a forum error of

Exception - Argument 2 passed to mod_forum\local\entities\author::__construct() must be of the type int, string given, called in [dirroot]/mod/forum/classes/local/factories/entity.php on line 184

The error is that the $user->picture field being passed to mod_forum\local\entities\author is a string instead of a int, which causes a TypeError to be thrown.

It took a while to trace down, but basically the attempts report in mod_h5pactivity modifies a local $user object, replacing the picture field with the rendered html picture field, so:

$user->picture == '1';

becomes

$user->picture == '<a href="https://moodle/user/view.php?id=123&amp;course=345" class="d-inline-block aabtn"><img src="https://moodle/theme/image.php/boost/core/1601249177/u/f2" class="userpicture defaultuserpic" width="35" height="35" alt="Picture of Some Student" title="Picture of Some Student" /></a>';

To reproduce:

1. As a student, make sure you have posted to a forum
2. Complete a mod_h5pactivity attempt (or have an attempt already existing)
3. Once you have an attempt, if you go to the activity, you will have 'View my attempts'
4. Click 'View my attempts'
5. Now navigate back to the forum discussion you have posted in previously
6. See the error above