May be it crossed into an area of space where physics is different.

A big unknown planet has crossed the path between Voyager 1 and the Earth, blocking the radio signals for 2 days !

(This is not impossible, because a planet so far away would have an extremely low angular velocity, so an occultation could take so long even for a not very big planet.)

If we are speculating, why be so uninteresting?

Maybe it was waiting to go through the inter-solar customs line to get out.

Maybe it has gained sentience on its own and is trying to awaken other space probes.