Issue with "As long as you control" creatures that are being controlled by a player other than the owner

On two separate occasions with two separate sets of cards, a player within my EDH pod would gain control of a card that had a "**for as long as you control X**" creature, and its effect would fail to resolve when the correct conditions became true. In the first example, a **roil elemental was taken via Sower of temptation's enter the battlefield effect**. Afterword, a land was played by the new controller of Roil Elemental which says "**Landfall - when a land enters the battlefield under your control, you may gain control of target creature for as long as you control roil elemental**". The prompt was given to the controller, who selected yes. The creature targeted by roil elemental did not have its' control changed to the current owner of roil elemental. Because the game would have ended with this play, we allowed it to continue for testing purposes, and the effect happened multiple times with each land drop made by the new controller. In the second example, an Olivia Voldaren was reanimated from an opponents' graveyard using the scarab god's activated ability. A vampire was targeted by Olivia Voldaren's second activated ability which states "**3BB: Gain control of target vampire for as long as you control Olivia Voldaren**". It was a legal target, and the ability was allowed to resolve. The control of the targeted vampire was not changed to the current owner of Olivia Voldaren as it should have been.

Thanks for all you guys do! Be safe :)