I don't believe there's any fix, but it would seem reasonable to me that Craig as Tour Director and judge takes into account whether or not the celeb is doing the tour when deciding who to save.
I'm not saying it's the only criteria he considers, just that it will be one of several. Of course he would never say it out loud, he'd just voice the other criteria he took into account.
There was one DO this year where he didn't say the usual words along the lines of "the couple I'm going to save because I thought they danced better in the DO is...". It hit me straight away and has stuck in my mind, but I can't remember who he was saving, so I don't know if they were doing the tour or not. IIRC he wasn't the only judge that week to change the way their decision was made.
So no conspiracy theory, but understandable business decision.