When the problems occur:
1. Signet of the Beastmaster is traited. (“Active effects of signets also affect you”).
2. Signet of the Wild utility skill has been activated by the ranger.
Bugs:
1. Cannot stomp downed enemies.
2. Cannot revive downed allies.
3. Cannot pickup environmental weapons.
In summary the interaction is not available and so you cannot click on F to do anything in PvP. Have not tested interactions in PvE.