Possible bug with Ruin + Turn Back the Clock?

Of course you can't use TBTC while Ruin is regressing the gen, but it should be possible while at least one survivor has his/her hands on a gen, right?
If yes, then there's a bug regarding this interaction.
No matter how many survs and which gen it is as long as Ruin is up you can't use TBTC. The game simply doesn't give you the prompt to do so.

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